81319531 has 2 divisors, whose sum is σ = 81319532. Its totient is φ = 81319530.

The previous prime is 81319457. The next prime is 81319577. The reversal of 81319531 is 13591318.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81319531 - 2⁹ = 81319019 is a prime.

It is a super-2 number, since 2×81319531² = 13225732244119922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81319493 and 81319502.

It is not a weakly prime, because it can be changed into another prime (81310531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40659765 + 40659766.

It is an arithmetic number, because the mean of its divisors is an integer number (40659766).

Almost surely, 2^81319531 is an apocalyptic number.

81319531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81319531 is an equidigital number, since it uses as much as digits as its factorization.

81319531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3240, while the sum is 31.

The square root of 81319531 is about 9017.7342497991. The cubic root of 81319531 is about 433.2430671286.

The spelling of 81319531 in words is "eighty-one million, three hundred nineteen thousand, five hundred thirty-one".