81537623999 has 4 divisors (see below), whose sum is σ = 87809748936. Its totient is φ = 75265499064.

The previous prime is 81537623989. The next prime is 81537624037. The reversal of 81537623999 is 99932673518.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81537623999 - 2²⁸ = 81269188543 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81537623989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3136062449 + ... + 3136062474.

It is an arithmetic number, because the mean of its divisors is an integer number (21952437234).

Almost surely, 2^81537623999 is an apocalyptic number.

81537623999 is a deficient number, since it is larger than the sum of its proper divisors (6272124937).

81537623999 is a wasteful number, since it uses less digits than its factorization.

81537623999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6272124936.

The product of its digits is 22044960, while the sum is 62.

The spelling of 81537623999 in words is "eighty-one billion, five hundred thirty-seven million, six hundred twenty-three thousand, nine hundred ninety-nine".