81313139 has 2 divisors, whose sum is σ = 81313140. Its totient is φ = 81313138.

The previous prime is 81313117. The next prime is 81313153. The reversal of 81313139 is 93131318.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81313139 - 2²⁰ = 80264563 is a prime.

It is a super-2 number, since 2×81313139² = 13223653148066642, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81313109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40656569 + 40656570.

It is an arithmetic number, because the mean of its divisors is an integer number (40656570).

Almost surely, 2^81313139 is an apocalyptic number.

81313139 is a deficient number, since it is larger than the sum of its proper divisors (1).

81313139 is an equidigital number, since it uses as much as digits as its factorization.

81313139 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1944, while the sum is 29.

The square root of 81313139 is about 9017.3798300837. The cubic root of 81313139 is about 433.2317153569.

The spelling of 81313139 in words is "eighty-one million, three hundred thirteen thousand, one hundred thirty-nine".