81915133 has 2 divisors, whose sum is σ = 81915134. Its totient is φ = 81915132.

The previous prime is 81915109. The next prime is 81915139. The reversal of 81915133 is 33151918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72539289 + 9375844 = 8517^2 + 3062^2 .

It is a cyclic number.

It is not a de Polignac number, because 81915133 - 2¹³ = 81906941 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81915095 and 81915104.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81915139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40957566 + 40957567.

It is an arithmetic number, because the mean of its divisors is an integer number (40957567).

Almost surely, 2^81915133 is an apocalyptic number.

It is an amenable number.

81915133 is a deficient number, since it is larger than the sum of its proper divisors (1).

81915133 is an equidigital number, since it uses as much as digits as its factorization.

81915133 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 81915133 is about 9050.6979288892. The cubic root of 81915133 is about 434.2982175275.

The spelling of 81915133 in words is "eighty-one million, nine hundred fifteen thousand, one hundred thirty-three".