Number 69

A page of the Numeropedia - the Special Encyclopedia of Numbers

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[Chemistry]  The atomic number of Thulium, Tm. An element in the Lanthanide series: Lanthanum (57) to Lutetium (71).

[EECS]  69Hexadecimal = 105Decimal and 105Octal = 69Decimal

[History]  The age of the 40th U.S. President Ronald Wilson Reagan when he was inaugurated (1981-1988), the oldest U.S. President. He was born on 6 February 1911.

[History]  The number of members of the U.S. Congress who cast their ballots to elect George Washington the first President of the Unites States on 04 February, 1789.

[Math.]  The square and cube of 69 use all 10 digits 0-9 once: 692 = 4,761 and 693 = 328,509.

[Math.]  23×64 = 1,472 = 32×46

23×96 = 2,208 = 32×69

64×69 = 4,416 = 96×46.

[Math.]  6932 = 6969.007…×1055.

[Math.]  "Rule of 69", "Rule of 70" and "Rule of 72" are used in accounting to compute the time interval for a principal to double for a compound interest rate r. Since t = ln2/ln(1+r) = 0.693147/r, those rules state that value of t can be approximated by 0.69/r for low interest rates or more calculating-conveniently 0.70/r or 0.72/r for higher typical rates (such 5% to 10%).

[Sport]  The standard circumference of a FIFA-approved soccer ball is 69 centimeters (68.5 - 69.5 cm). (FIFA: Federation Internationale de Football Association)

64, 66, 67, 68 & 69

[Math.]

 66×64 = 4224 66×67 = 4422 66×68 = 4488 66×69 = 4554 66×74 = 4884

 666×661 = 440,226 666×666 = 443,556 666×669 = 445,554 666×672 = 447,552 666×663 = 441,558 666×667 = 444,222 666×670 = 446,220 666×674 = 448,884 666×664 = 442,224 666×668 = 444,888 666×671 = 446,886 666×675 = 449,550

… (generalizable pattern) …