81137909 has 2 divisors, whose sum is σ = 81137910. Its totient is φ = 81137908.

The previous prime is 81137897. The next prime is 81137971. The reversal of 81137909 is 90973118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65966884 + 15171025 = 8122^2 + 3895^2 .

It is a cyclic number.

It is not a de Polignac number, because 81137909 - 2⁸ = 81137653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81137989) 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, 40568954 + 40568955.

It is an arithmetic number, because the mean of its divisors is an integer number (40568955).

Almost surely, 2^81137909 is an apocalyptic number.

It is an amenable number.

81137909 is a deficient number, since it is larger than the sum of its proper divisors (1).

81137909 is an equidigital number, since it uses as much as digits as its factorization.

81137909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13608, while the sum is 38.

The square root of 81137909 is about 9007.6583527574. The cubic root of 81137909 is about 432.9202864281.

The spelling of 81137909 in words is "eighty-one million, one hundred thirty-seven thousand, nine hundred nine".