Number 61

A page of the Numeropedia - the Special Encyclopedia of Numbers

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[Chem.]  The atomic number of Promethium (Pm). An element in the Lanthanide series: Lanthanum (57) to Lutetium (71).

[Chem.]  Elements with atomic number 43 (Technetium, Tc), 61 (Promethium, Pm) and from 84 (Polonium, Po) up are radioactive.

[Chem.]  Elements with atomic number 43 (Technetium, Tc), 61 (Promethium, Pm) and from 93 (Neptunium, Np) up are artificial (not or no longer accruing on Earth).

[Game]  The total number of questions in all 3 stages of the TV’s “Jeopardy!” show: 30 in each of the first 2 stages and 1 in the final “Jeopardy!”.

[Math.]  A prime number.

A Mersenne exponent: 261–1 is the 9th Mersenne prime number.

[Math.]  614 = 13,845,841 = (1+38+4+5+8+4+1)4.

[Math.]  Euler numbers (or secant numbers Ei) are defined by the infinite series: sec(x) = 1/cos(x) = 1+E2(x2/2!)+E4(x4/4!)+E6(x6/6!)+…, where E0 = 1, E2 = –1, E4 = 5, E6 =  61, E8 = 1,385, E10 = –50,521, E12 = 2,702,765, E14 = –199,360,981, E16 = 19,391,512,145, E18 = –2,404,879,675,441… The odd-indexed Euler numbers are all 0. The even-indexed Euler numbers have alternating signs.

[Math.]  The 5th Keith number: 6, 1, 7, 8, 15, 23, 38, 61, 99…

[Movie]  Name of TV show/series or movie: “61*”.

[Phone]  International telephone dialing code for Australia, including external territories of Christmas Island and Cocos Islands.

[Phone]  The emergency telephone numbers dialing within Spain are 061 or 532.

[Sport]  The size of an ice hockey rink: 200 feet long & 85 feet wide (or 61 meters long and 25.9 meters wide).

[Measure]  1 l (liters) = 61.023744 inch3.

U.S. customary units for liquid measures: 1 gallon = 4 quarts = 8 pints = 32 gills = 128 fluid ounces = 1024 fluid drams = 61440 minims = 3.785411784 liters = 231 inch3.