81331409 has 2 divisors, whose sum is σ = 81331410. Its totient is φ = 81331408.

The previous prime is 81331403. The next prime is 81331433. The reversal of 81331409 is 90413318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 44849809 + 36481600 = 6697^2 + 6040^2 .

It is a cyclic number.

It is not a de Polignac number, because 81331409 - 2²⁰ = 80282833 is a prime.

It is a super-2 number, since 2×81331409² = 13229596179850562, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81331403) 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, 40665704 + 40665705.

It is an arithmetic number, because the mean of its divisors is an integer number (40665705).

Almost surely, 2^81331409 is an apocalyptic number.

It is an amenable number.

81331409 is a deficient number, since it is larger than the sum of its proper divisors (1).

81331409 is an equidigital number, since it uses as much as digits as its factorization.

81331409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 81331409 is about 9018.3928169048. The cubic root of 81331409 is about 433.2641600958.

The spelling of 81331409 in words is "eighty-one million, three hundred thirty-one thousand, four hundred nine".