81375515 has 16 divisors (see below), whose sum is σ = 111349728. Its totient is φ = 56557056.

The previous prime is 81375493. The next prime is 81375521. The reversal of 81375515 is 51557318.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81375515 is a prime.

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, 35717 + ... + 37926.

It is an arithmetic number, because the mean of its divisors is an integer number (6959358).

Almost surely, 2^81375515 is an apocalyptic number.

81375515 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81375515 is a deficient number, since it is larger than the sum of its proper divisors (29974213).

81375515 is a wasteful number, since it uses less digits than its factorization.

81375515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73678.

The product of its digits is 21000, while the sum is 35.

The square root of 81375515 is about 9020.8378214000. The cubic root of 81375515 is about 433.3424656195.

The spelling of 81375515 in words is "eighty-one million, three hundred seventy-five thousand, five hundred fifteen".