81681773220 has 48 divisors (see below), whose sum is σ = 254121073920. Its totient is φ = 21781806048.

The previous prime is 81681773209. The next prime is 81681773269. The reversal of 81681773220 is 2237718618.

It is a Harshad number since it is a multiple of its sum of digits (45).

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, 75630732 + ... + 75631811.

It is an arithmetic number, because the mean of its divisors is an integer number (5294189040).

Almost surely, 2^81681773220 is an apocalyptic number.

It is an amenable number.

81681773220 is an abundant number, since it is smaller than the sum of its proper divisors (172439300700).

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

81681773220 is a wasteful number, since it uses less digits than its factorization.

81681773220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151262561 (or 151262553 counting only the distinct ones).

The product of its (nonzero) digits is 225792, while the sum is 45.

The spelling of 81681773220 in words is "eighty-one billion, six hundred eighty-one million, seven hundred seventy-three thousand, two hundred twenty".