81123915 has 32 divisors (see below), whose sum is σ = 139207680. Its totient is φ = 40195584.

The previous prime is 81123899. The next prime is 81124007. The reversal of 81123915 is 51932118.

It is not a de Polignac number, because 81123915 - 2⁴ = 81123899 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 18132 + ... + 22158.

It is an arithmetic number, because the mean of its divisors is an integer number (4350240).

Almost surely, 2^81123915 is an apocalyptic number.

81123915 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81123915 is a deficient number, since it is larger than the sum of its proper divisors (58083765).

81123915 is a wasteful number, since it uses less digits than its factorization.

81123915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4131.

The product of its digits is 2160, while the sum is 30.

The square root of 81123915 is about 9006.8815358036. The cubic root of 81123915 is about 432.8953961522.

The spelling of 81123915 in words is "eighty-one million, one hundred twenty-three thousand, nine hundred fifteen".