81351581975 has 24 divisors (see below), whose sum is σ = 106930754208. Its totient is φ = 61183616000.

The previous prime is 81351581957. The next prime is 81351581989. The reversal of 81351581975 is 57918515318.

It is a de Polignac number, because none of the positive numbers 2^k-81351581975 is a prime.

It is a hoax number, since the sum of its digits (53) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

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, 269075 + ... + 484875.

It is an arithmetic number, because the mean of its divisors is an integer number (4455448092).

Almost surely, 2^81351581975 is an apocalyptic number.

81351581975 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81351581975 is a deficient number, since it is larger than the sum of its proper divisors (25579172233).

81351581975 is a wasteful number, since it uses less digits than its factorization.

81351581975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216715 (or 216710 counting only the distinct ones).

The product of its digits is 1512000, while the sum is 53.

The spelling of 81351581975 in words is "eighty-one billion, three hundred fifty-one million, five hundred eighty-one thousand, nine hundred seventy-five".