81912959 has 4 divisors (see below), whose sum is σ = 85474416. Its totient is φ = 78351504.

The previous prime is 81912947. The next prime is 81912983. The reversal of 81912959 is 95921918.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81912959 - 2¹² = 81908863 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81915959) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1780694 + ... + 1780739.

It is an arithmetic number, because the mean of its divisors is an integer number (21368604).

Almost surely, 2^81912959 is an apocalyptic number.

81912959 is a deficient number, since it is larger than the sum of its proper divisors (3561457).

81912959 is a wasteful number, since it uses less digits than its factorization.

81912959 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3561456.

The product of its digits is 58320, while the sum is 44.

The square root of 81912959 is about 9050.5778268572. The cubic root of 81912959 is about 434.2943754507.

The spelling of 81912959 in words is "eighty-one million, nine hundred twelve thousand, nine hundred fifty-nine".