81656487 has 36 divisors (see below), whose sum is σ = 130712400. Its totient is φ = 49082880.

The previous prime is 81656483. The next prime is 81656539. The reversal of 81656487 is 78465618.

It is a happy number.

81656487 is a `hidden beast` number, since 8 + 1 + 6 + 564 + 87 = 666.

It is not a de Polignac number, because 81656487 - 2² = 81656483 is a prime.

Its product of digits (322560) is a multiple of the sum of its prime divisors (630).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81656483) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 181639 + ... + 182087.

It is an arithmetic number, because the mean of its divisors is an integer number (3630900).

Almost surely, 2^81656487 is an apocalyptic number.

81656487 is a deficient number, since it is larger than the sum of its proper divisors (49055913).

81656487 is a wasteful number, since it uses less digits than its factorization.

81656487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 644 (or 630 counting only the distinct ones).

The product of its digits is 322560, while the sum is 45.

The square root of 81656487 is about 9036.3978996058. The cubic root of 81656487 is about 433.8406385397.

The spelling of 81656487 in words is "eighty-one million, six hundred fifty-six thousand, four hundred eighty-seven".