81863556 has 12 divisors (see below), whose sum is σ = 191014992. Its totient is φ = 27287848.

The previous prime is 81863543. The next prime is 81863563. The reversal of 81863556 is 65536818.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3410970 + ... + 3410993.

It is an arithmetic number, because the mean of its divisors is an integer number (15917916).

Almost surely, 2^81863556 is an apocalyptic number.

It is an amenable number.

81863556 is an abundant number, since it is smaller than the sum of its proper divisors (109151436).

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

81863556 is a wasteful number, since it uses less digits than its factorization.

81863556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6821970 (or 6821968 counting only the distinct ones).

The product of its digits is 172800, while the sum is 42.

The square root of 81863556 is about 9047.8481419617. The cubic root of 81863556 is about 434.2070479586.

The spelling of 81863556 in words is "eighty-one million, eight hundred sixty-three thousand, five hundred fifty-six".