81939601 has 2 divisors, whose sum is σ = 81939602. Its totient is φ = 81939600.

The previous prime is 81939569. The next prime is 81939617. The reversal of 81939601 is 10693918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81018001 + 921600 = 9001^2 + 960^2 .

It is a cyclic number.

It is not a de Polignac number, because 81939601 - 2⁵ = 81939569 is a prime.

It is not a weakly prime, because it can be changed into another prime (81939631) 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, 40969800 + 40969801.

It is an arithmetic number, because the mean of its divisors is an integer number (40969801).

Almost surely, 2^81939601 is an apocalyptic number.

It is an amenable number.

81939601 is a deficient number, since it is larger than the sum of its proper divisors (1).

81939601 is an equidigital number, since it uses as much as digits as its factorization.

81939601 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11664, while the sum is 37.

The square root of 81939601 is about 9052.0495469258. The cubic root of 81939601 is about 434.3414547599.

The spelling of 81939601 in words is "eighty-one million, nine hundred thirty-nine thousand, six hundred one".