81912497956 has 6 divisors (see below), whose sum is σ = 143346871430. Its totient is φ = 40956248976.

The previous prime is 81912497941. The next prime is 81912497971. The reversal of 81912497956 is 65979421918.

It is an interprime number because it is at equal distance from previous prime (81912497941) and next prime (81912497971).

It can be written as a sum of positive squares in only one way, i.e., 81690785856 + 221712100 = 285816^2 + 14890^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81912497894 and 81912497903.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10239062241 + ... + 10239062248.

Almost surely, 2^81912497956 is an apocalyptic number.

It is an amenable number.

81912497956 is a deficient number, since it is larger than the sum of its proper divisors (61434373474).

81912497956 is a wasteful number, since it uses less digits than its factorization.

81912497956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20478124493 (or 20478124491 counting only the distinct ones).

The product of its digits is 9797760, while the sum is 61.

The spelling of 81912497956 in words is "eighty-one billion, nine hundred twelve million, four hundred ninety-seven thousand, nine hundred fifty-six".