81310531 has 2 divisors, whose sum is σ = 81310532. Its totient is φ = 81310530.

The previous prime is 81310511. The next prime is 81310547. The reversal of 81310531 is 13501318.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81310531 - 2¹⁹ = 80786243 is a prime.

It is a super-2 number, since 2×81310531² = 13222804903003922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81310511) 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 as a sum of consecutive naturals, namely, 40655265 + 40655266.

It is an arithmetic number, because the mean of its divisors is an integer number (40655266).

Almost surely, 2^81310531 is an apocalyptic number.

81310531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81310531 is an equidigital number, since it uses as much as digits as its factorization.

81310531 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 81310531 is about 9017.2352192898. The cubic root of 81310531 is about 433.2270835495.

Adding to 81310531 its reverse (13501318), we get a palindrome (94811849).

The spelling of 81310531 in words is "eighty-one million, three hundred ten thousand, five hundred thirty-one".