81320873 has 2 divisors, whose sum is σ = 81320874. Its totient is φ = 81320872.

The previous prime is 81320807. The next prime is 81320879. The reversal of 81320873 is 37802318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79352464 + 1968409 = 8908^2 + 1403^2 .

It is a cyclic number.

It is not a de Polignac number, because 81320873 - 2¹² = 81316777 is a prime.

It is a super-2 number, since 2×81320873² = 13226168770964258, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81320879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40660436 + 40660437.

It is an arithmetic number, because the mean of its divisors is an integer number (40660437).

Almost surely, 2^81320873 is an apocalyptic number.

It is an amenable number.

81320873 is a deficient number, since it is larger than the sum of its proper divisors (1).

81320873 is an equidigital number, since it uses as much as digits as its factorization.

81320873 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 81320873 is about 9017.8086584269. The cubic root of 81320873 is about 433.2454503568.

The spelling of 81320873 in words is "eighty-one million, three hundred twenty thousand, eight hundred seventy-three".