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Seventy-two is a pronic number, as it is the product of 8 and 9. [1] It is the smallest Achilles number, as it's a powerful number that is not itself a power. [2] 72 is an abundant number. [3] With exactly twelve positive divisors, including 12 (one of only two sublime numbers), [4] 72 is also the twelfth member in the sequence of refactorable ...
The basic rule for divisibility by 4 is that if the number formed by the last two digits in a number is divisible by 4, the original number is divisible by 4; [2] [3] this is because 100 is divisible by 4 and so adding hundreds, thousands, etc. is simply adding another number that is divisible by 4. If any number ends in a two digit number that ...
The natural log of 2 is 0.693147, so when you solve for t using those natural logarithms, you get t = 0.693147/r.. The actual results aren’t round numbers and are closer to 69.3, but 72 easily ...
d() is the number of positive divisors of n, including 1 and n itself; σ() is the sum of the positive divisors of n, including 1 and n itselfs() is the sum of the proper divisors of n, including 1 but not n itself; that is, s(n) = σ(n) − n
Both 2 2 = 4 and 3 2 = 9 are divisors of 108. However, 108 cannot be represented as m k, where m and k are positive integers greater than 1, so 108 is an Achilles number. The integer 360 is not an Achilles number because it is not powerful. One of its prime factors is 5 but 360 is not divisible by 5 2 = 25. Finally, 784 is not an Achilles number.
The smallest odd integer with abundancy index exceeding 3 is 1018976683725 = 3 3 × 5 2 × 7 2 × 11 × 13 × 17 × 19 × 23 × 29. [8] If p = (p 1, ..., p n) is a list of primes, then p is termed abundant if some integer composed only of primes in p is abundant. A necessary and sufficient condition for this is that the product of p i /(p i − ...
In finance, the rule of 72, the rule of 70 [1] and the rule of 69.3 are methods for estimating an investment's doubling time. The rule number (e.g., 72) is divided by the interest percentage per period (usually years) to obtain the approximate number of periods required for doubling.
Prime numbers have exactly 2 divisors, and highly composite numbers are in bold. 7 is a divisor of 42 because =, so we can say It can also be said that 42 is divisible by 7, 42 is a multiple of 7, 7 divides 42, or 7 is a factor of 42. The non-trivial divisors of 6 are 2, −2, 3, −3.