81388215 has 12 divisors (see below), whose sum is σ = 141072984. Its totient is φ = 43407024.

The previous prime is 81388169. The next prime is 81388247. The reversal of 81388215 is 51288318.

It is not a de Polignac number, because 81388215 - 2⁹ = 81387703 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81388215.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 904269 + ... + 904358.

It is an arithmetic number, because the mean of its divisors is an integer number (11756082).

Almost surely, 2^81388215 is an apocalyptic number.

81388215 is a deficient number, since it is larger than the sum of its proper divisors (59684769).

81388215 is a wasteful number, since it uses less digits than its factorization.

81388215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1808638 (or 1808635 counting only the distinct ones).

The product of its digits is 15360, while the sum is 36.

The square root of 81388215 is about 9021.5417196841. The cubic root of 81388215 is about 433.3650078754.

The spelling of 81388215 in words is "eighty-one million, three hundred eighty-eight thousand, two hundred fifteen".