81791831 has 4 divisors (see below), whose sum is σ = 89227464. Its totient is φ = 74356200.

The previous prime is 81791807. The next prime is 81791833. The reversal of 81791831 is 13819718.

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 81791831 - 2⁶ = 81791767 is a prime.

It is a super-2 number, since 2×81791831² = 13379807236665122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81791833) 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, 3717800 + ... + 3717821.

It is an arithmetic number, because the mean of its divisors is an integer number (22306866).

Almost surely, 2^81791831 is an apocalyptic number.

81791831 is a deficient number, since it is larger than the sum of its proper divisors (7435633).

81791831 is a wasteful number, since it uses less digits than its factorization.

81791831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7435632.

The product of its digits is 12096, while the sum is 38.

The square root of 81791831 is about 9043.8836237537. The cubic root of 81791831 is about 434.0802003032.

The spelling of 81791831 in words is "eighty-one million, seven hundred ninety-one thousand, eight hundred thirty-one".