81312013 has 2 divisors, whose sum is σ = 81312014. Its totient is φ = 81312012.

The previous prime is 81311987. The next prime is 81312031. The reversal of 81312013 is 31021318.

Together with next prime (81312031) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 42536484 + 38775529 = 6522^2 + 6227^2 .

It is a cyclic number.

It is not a de Polignac number, because 81312013 - 2⁹ = 81311501 is a prime.

It is a super-2 number, since 2×81312013² = 13223286916224338, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81312083) 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, 40656006 + 40656007.

It is an arithmetic number, because the mean of its divisors is an integer number (40656007).

Almost surely, 2^81312013 is an apocalyptic number.

It is an amenable number.

81312013 is a deficient number, since it is larger than the sum of its proper divisors (1).

81312013 is an equidigital number, since it uses as much as digits as its factorization.

81312013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 81312013 is about 9017.3173948797. The cubic root of 81312013 is about 433.2297155933.

The spelling of 81312013 in words is "eighty-one million, three hundred twelve thousand, thirteen".