Number 99

A page of the Numeropedia - the Special Encyclopedia of Numbers

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[Chemistry]  The atomic number of Einsteinium (Es). An element in the Actinide series: Actinium (89) to Lawrencium (103).

[Math.]  Its odd powers end with 99. Its even powers end with 01.

[Math.]  99 = 23+33+43.

[Math.]

992 = 9801 = (98+01)2

993 = 970,299 = (9+70+2+9+9)3

995 = 9,509,900,499 = (9+50+9+9+0+0+4+9+9)5

996 = 941,480,149,401 = (9+4+14+8+0+14+9+40+1)6

997 = 93,206,534,790,699 = (9+32+0+6+5+3+4+7+9+0+6+9+9)7.

[Math.]

(*)   332×9 = 1089×9 = 9,801 = 992 & 1089×9801 = 10,673,289 = 32672

1089…1089×9 = 9801…9801  & 1089…1089×9801…9801  = 3267…32672

(**)  10989×9 = 98901 & 10989×98901 = 1,086,823,089 = 329672

10989…10989×9 = 98901…98901 & 10989…10989×98901...98901 = 32967…329672

(***)   109989×9 = 989901 & 109989×989901 = 108,878,221,089 = 3299672

109989…109989×9 = 989901…989901 &

109989…109989×989901...989901 = 329967…3299672

(****)  109…989×9 = 989…901 & 109...989×989…901 = 329…9672

109…989...109…989×9 = 989…901...989…901  &

109…989…109…989×989…901...989…901 = 329…967…329…9672.

[Math.]  A well-know, even complicated,  formula: arctan(1/239) = 4×arctan(1/5)–p/4 = arctan(1/70)–arctan(1/99) = arctan(1/408)+arctan(1/577).

[Money]  The value 99 cents is the most popular value within the prices for U.S. products and goods before taxes.

[Phone]  The number to key in text messaging on telephone keypad for letter X.

[Phone]  The last 2 digits of an NANPA/U.S. area code cannot be the same, i.e. cannot be: 11, 22, 33, 44, 55, 66, 77, 88 or 99. (NANPA: North American Numbering Plan Administration).

[Tech.]  The “number system” code of an EAN-13 barcode for common currency coupons: 99, 981 and 982.

[Trivia]  The largest 2-digit number or the maximum number that can be displayed by a 2-digit counter.