81329787 has 72 divisors (see below), whose sum is σ = 151377408. Its totient is φ = 41168160.

The previous prime is 81329777. The next prime is 81329839. The reversal of 81329787 is 78792318.

It is not a de Polignac number, because 81329787 - 2¹⁸ = 81067643 is a prime.

It is a super-2 number, since 2×81329787² = 13229068506930738, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81329767) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 358168 + ... + 358394.

It is an arithmetic number, because the mean of its divisors is an integer number (2102464).

Almost surely, 2^81329787 is an apocalyptic number.

81329787 is a deficient number, since it is larger than the sum of its proper divisors (70047621).

81329787 is a wasteful number, since it uses less digits than its factorization.

81329787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 309 (or 295 counting only the distinct ones).

The product of its digits is 169344, while the sum is 45.

The square root of 81329787 is about 9018.3028891250. The cubic root of 81329787 is about 433.2612798673.

The spelling of 81329787 in words is "eighty-one million, three hundred twenty-nine thousand, seven hundred eighty-seven".