81820915 has 16 divisors (see below), whose sum is σ = 113412960. Its totient is φ = 56005120.

The previous prime is 81820909. The next prime is 81820931. The reversal of 81820915 is 51902818.

It is not a de Polignac number, because 81820915 - 2¹⁷ = 81689843 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, 42820 + ... + 44689.

It is an arithmetic number, because the mean of its divisors is an integer number (7088310).

Almost surely, 2^81820915 is an apocalyptic number.

81820915 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81820915 is a deficient number, since it is larger than the sum of its proper divisors (31592045).

81820915 is a wasteful number, since it uses less digits than its factorization.

81820915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87542.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 81820915 is about 9045.4914183808. The cubic root of 81820915 is about 434.1316451002.

The spelling of 81820915 in words is "eighty-one million, eight hundred twenty thousand, nine hundred fifteen".