81557339 has 2 divisors, whose sum is σ = 81557340. Its totient is φ = 81557338.

The previous prime is 81557321. The next prime is 81557363. The reversal of 81557339 is 93375518.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81557339 - 2⁸ = 81557083 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 81557296 and 81557305.

It is not a weakly prime, because it can be changed into another prime (81557239) 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, 40778669 + 40778670.

It is an arithmetic number, because the mean of its divisors is an integer number (40778670).

Almost surely, 2^81557339 is an apocalyptic number.

81557339 is a deficient number, since it is larger than the sum of its proper divisors (1).

81557339 is an equidigital number, since it uses as much as digits as its factorization.

81557339 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 113400, while the sum is 41.

The square root of 81557339 is about 9030.9101977597. The cubic root of 81557339 is about 433.6649764278.

The spelling of 81557339 in words is "eighty-one million, five hundred fifty-seven thousand, three hundred thirty-nine".