81631668 has 24 divisors (see below), whose sum is σ = 194527872. Its totient is φ = 26631424.

The previous prime is 81631651. The next prime is 81631687. The reversal of 81631668 is 86613618.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 71805 + ... + 72932.

It is an arithmetic number, because the mean of its divisors is an integer number (8105328).

Almost surely, 2^81631668 is an apocalyptic number.

It is an amenable number.

81631668 is an abundant number, since it is smaller than the sum of its proper divisors (112896204).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81631668 is a wasteful number, since it uses less digits than its factorization.

81631668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144791 (or 144789 counting only the distinct ones).

The product of its digits is 41472, while the sum is 39.

The square root of 81631668 is about 9035.0245157387. The cubic root of 81631668 is about 433.7966796648.

The spelling of 81631668 in words is "eighty-one million, six hundred thirty-one thousand, six hundred sixty-eight".