81138313 has 2 divisors, whose sum is σ = 81138314. Its totient is φ = 81138312.

The previous prime is 81138307. The next prime is 81138347. The reversal of 81138313 is 31383118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65480464 + 15657849 = 8092^2 + 3957^2 .

It is a cyclic number.

It is not a de Polignac number, because 81138313 - 2²¹ = 79041161 is a prime.

It is not a weakly prime, because it can be changed into another prime (81138383) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40569156 + 40569157.

It is an arithmetic number, because the mean of its divisors is an integer number (40569157).

Almost surely, 2^81138313 is an apocalyptic number.

It is an amenable number.

81138313 is a deficient number, since it is larger than the sum of its proper divisors (1).

81138313 is an equidigital number, since it uses as much as digits as its factorization.

81138313 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 28.

The square root of 81138313 is about 9007.6807780916. The cubic root of 81138313 is about 432.9210049558.

The spelling of 81138313 in words is "eighty-one million, one hundred thirty-eight thousand, three hundred thirteen".