81307993 has 16 divisors (see below), whose sum is σ = 89582976. Its totient is φ = 73342080.

The previous prime is 81307987. The next prime is 81308021. The reversal of 81307993 is 39970318.

It is a cyclic number.

It is not a de Polignac number, because 81307993 - 2²¹ = 79210841 is a prime.

It is a super-2 number, since 2×81307993² = 13221979451376098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81307943) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 126130 + ... + 126772.

It is an arithmetic number, because the mean of its divisors is an integer number (5598936).

Almost surely, 2^81307993 is an apocalyptic number.

It is an amenable number.

81307993 is a deficient number, since it is larger than the sum of its proper divisors (8274983).

81307993 is a wasteful number, since it uses less digits than its factorization.

81307993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 864.

The product of its (nonzero) digits is 40824, while the sum is 40.

The square root of 81307993 is about 9017.0944876939. The cubic root of 81307993 is about 433.2225759670. Note that the first 3 decimals are identical.

The spelling of 81307993 in words is "eighty-one million, three hundred seven thousand, nine hundred ninety-three".