81971556 has 48 divisors (see below), whose sum is σ = 196320768. Its totient is φ = 26611200.

The previous prime is 81971537. The next prime is 81971557. The reversal of 81971556 is 65517918.

It is a super-2 number, since 2×81971556² = 13438671986122272, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81971557) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 82221 + ... + 83211.

It is an arithmetic number, because the mean of its divisors is an integer number (4090016).

Almost surely, 2^81971556 is an apocalyptic number.

It is an amenable number.

81971556 is an abundant number, since it is smaller than the sum of its proper divisors (114349212).

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

81971556 is a wasteful number, since it uses less digits than its factorization.

81971556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1172 (or 1170 counting only the distinct ones).

The product of its digits is 75600, while the sum is 42.

The square root of 81971556 is about 9053.8144447520. The cubic root of 81971556 is about 434.3979092587.

The spelling of 81971556 in words is "eighty-one million, nine hundred seventy-one thousand, five hundred fifty-six".