81631892 has 24 divisors (see below), whose sum is σ = 151552296. Its totient is φ = 38340608.

The previous prime is 81631871. The next prime is 81631919. The reversal of 81631892 is 29813618.

It can be written as a sum of positive squares in 4 ways, for example, as 163216 + 81468676 = 404^2 + 9026^2 .

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, 51788 + ... + 53340.

It is an arithmetic number, because the mean of its divisors is an integer number (6314679).

Almost surely, 2^81631892 is an apocalyptic number.

It is an amenable number.

81631892 is a deficient number, since it is larger than the sum of its proper divisors (69920404).

81631892 is a wasteful number, since it uses less digits than its factorization.

81631892 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2347 (or 2345 counting only the distinct ones).

The product of its digits is 20736, while the sum is 38.

The square root of 81631892 is about 9035.0369119335. The cubic root of 81631892 is about 433.7970764486.

The spelling of 81631892 in words is "eighty-one million, six hundred thirty-one thousand, eight hundred ninety-two".