81385939 has 2 divisors, whose sum is σ = 81385940. Its totient is φ = 81385938.

The previous prime is 81385933. The next prime is 81385963. The reversal of 81385939 is 93958318.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81385939 - 2²⁵ = 47831507 is a prime.

It is not a weakly prime, because it can be changed into another prime (81385933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40692969 + 40692970.

It is an arithmetic number, because the mean of its divisors is an integer number (40692970).

Almost surely, 2^81385939 is an apocalyptic number.

81385939 is a deficient number, since it is larger than the sum of its proper divisors (1).

81385939 is an equidigital number, since it uses as much as digits as its factorization.

81385939 is an evil number, because the sum of its binary digits is even.

The product of its digits is 233280, while the sum is 46.

The square root of 81385939 is about 9021.4155762829. The cubic root of 81385939 is about 433.3609681916.

The spelling of 81385939 in words is "eighty-one million, three hundred eighty-five thousand, nine hundred thirty-nine".