990

[Math.]  A triangular number (sum of all integers from 1 to 44): 990 = 1+2+…+43+44.

 

[Math.]  A pair of triangular numbers 780 and 990 whose sum (1770) and difference (210) are also triangular: 780 = 1+2+…+38+39, 210 = 1+2+…+19+20 and 1770 = 1+2+…+58+59.

 

[Math.]  (Sequence of numbers: (10n–10m, n > 2m).

9902 = 980,100 = (980+10+0)2.

 

[Math.]   10,100 = 102+1002 and 990,100 = 9902+1002, where 990+10 = 1000.

 

[Phone] The emergency telephone numbers dialing within Trinidad and Tobago  are 990 and 999.

 

991

[Math.]  An absolute prime number (or permutable prime number): all 3 numbers 991, 919 and 199 are prime or in fact, absolute prime.

 

[Math.]  Circular prime numbers: all 3 numbers 991, 919 and 199 are prime.

 

[Math.]  (Sequence of numbers (10n–9), n > 1):

9912 = 982,081 = (982+0+8+1)2.

9913 = 973,242,271 = (973+2+4+2+2+7+1)3.

 

[Phone]  The emergency telephone number dialing within Liberia (cell phones only).

 

992

[Phone]  International telephone dialing code for Tajikistan.

 

993

[Chemistry]  The number of paraffins with 8 carbon atoms.

 

[Math.]  9933 = 979,146,657 = (979+14–(6+6)+(7+5))3.

 

[Phone]  International telephone dialing code for Turkmenistan.

 

994

[Literature]  The longest poem in the world, written by Patrick Huet (France) in 2006, “Pieces of Hope to the Echo of the World” has 7547 verses. It is an “acrostic” whose first letters of each verse spell out the text of 30 articles of the 1948 Universal Declaration of Human Rights. It is displayed on a roll of fabric of 3261 feet or about 994 meters.

 

[Math.]  

94 = 47×2 and, reversely, 49 = 47+2

994 = 497×2 and, reversely, 499 = 497+2

9994 = 4997×2 and, reversely, 4999 = 4997+2

99994 = 49997×2 and, reversely, 49999 = 49997+2

999,999,999,994 = 499,999,999,997×2 and, reversely,

499,999,999,999 = 499,999,999,997+2 …

 

[Phone]  International telephone dialing code for Azerbaijan.

 

[Phone]  The emergency telephone numbers dialing within Malaysia are 994 and 999.

 

995

[Math.]  9952 = 990,025. (Sequence of numbers (10n–5), n > 1).

 

[Phone]  International telephone dialing code for Georgia.

 

[Phone]  The emergency telephone numbers dialing within Singapore are 995 and 999.

 

[Tech.]  The approximate speed of Mach 3, (meters/second).

 

996

[Math.]  9962 = 992,016. (Sequence of numbers (10n–4), n > 1).

 

[Math.] 

962 = 9,216

9962 = 992,016

99962 = 99,920,016

99,9962 = 9,999,200,016

999,9962 = 999,992,000,016

 

[Phone]  International telephone dialing code for Kyrgyzstan.

 

997

[Math.]  The largest 3-digit prime number.

 

[Math.]   (Sequence of numbers (10n–3), n ³ 2).

9973 = 991,026,973 = (991+02–69+73)3

 

[Phone]  The emergency telephone number dialing within Poland.

 

[Phone]  The emergency telephone numbers dialing within Botswana  are 997 and 911.

 

998

[Math.]  (Sequence of  numbers (10n–2), n > 1).

9983 = 994,011,992 = (994+0+1+1+9–9+2)3

 

[Phone]  International telephone dialing code for Uzbekistan.

 

[Phone]  The emergency telephone numbers dialing within United Arab Emirates (Abu Dhabi are 998 and also 999.

 

999 (separate page)

 

91-99 & 991-999 & 9991-9999 & 99991-99999...

[Math.]  Repeatedly inserting number 9 before ab and number 0 before cdin the square number abcd = (9x)2yields the square numbers: (99x)2 = 9ab0cd; (999x)2 = 99ab00cd…, for x = 1 to 9.

 

991-999

[Library]  Numbers 900-999 are the first 3 digits in Dewey Decimal Classification System call numbers for library books in History and Geography. Numbers 990-999 are in History of less popular areas, such as Australia, Pacific Polynesia, Arctic and Antarctica…