81291957372 has 72 divisors (see below), whose sum is σ = 213149892592. Its totient is φ = 27090806400.

The previous prime is 81291957337. The next prime is 81291957403. The reversal of 81291957372 is 27375919218.

It is a happy number.

81291957372 is a `hidden beast` number, since 81 + 2 + 9 + 195 + 7 + 372 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5709222 + ... + 5723442.

Almost surely, 2^81291957372 is an apocalyptic number.

It is an amenable number.

81291957372 is an abundant number, since it is smaller than the sum of its proper divisors (131857935220).

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

81291957372 is a wasteful number, since it uses less digits than its factorization.

81291957372 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20121 (or 20107 counting only the distinct ones).

The product of its digits is 1905120, while the sum is 54.

The spelling of 81291957372 in words is "eighty-one billion, two hundred ninety-one million, nine hundred fifty-seven thousand, three hundred seventy-two".