81761993556 has 48 divisors (see below), whose sum is σ = 192100126848. Its totient is φ = 27065232000.

The previous prime is 81761993549. The next prime is 81761993563. The reversal of 81761993556 is 65539916718.

It is an interprime number because it is at equal distance from previous prime (81761993549) and next prime (81761993563).

It is a self number, because there is not a number n which added to its sum of digits gives 81761993556.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9659166 + ... + 9667626.

It is an arithmetic number, because the mean of its divisors is an integer number (4002085976).

Almost surely, 2^81761993556 is an apocalyptic number.

It is an amenable number.

81761993556 is an abundant number, since it is smaller than the sum of its proper divisors (110338133292).

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

81761993556 is a wasteful number, since it uses less digits than its factorization.

81761993556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13952 (or 13950 counting only the distinct ones).

The product of its digits is 12247200, while the sum is 60.

The spelling of 81761993556 in words is "eighty-one billion, seven hundred sixty-one million, nine hundred ninety-three thousand, five hundred fifty-six".