81957329 has 2 divisors, whose sum is σ = 81957330. Its totient is φ = 81957328.

The previous prime is 81957299. The next prime is 81957347. The reversal of 81957329 is 92375918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80066704 + 1890625 = 8948^2 + 1375^2 .

It is a cyclic number.

It is not a de Polignac number, because 81957329 - 2²⁴ = 65180113 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81957329.

It is not a weakly prime, because it can be changed into another prime (81957529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40978664 + 40978665.

It is an arithmetic number, because the mean of its divisors is an integer number (40978665).

Almost surely, 2^81957329 is an apocalyptic number.

It is an amenable number.

81957329 is a deficient number, since it is larger than the sum of its proper divisors (1).

81957329 is an equidigital number, since it uses as much as digits as its factorization.

81957329 is an evil number, because the sum of its binary digits is even.

The product of its digits is 136080, while the sum is 44.

The square root of 81957329 is about 9053.0287197158. The cubic root of 81957329 is about 434.3727764081.

The spelling of 81957329 in words is "eighty-one million, nine hundred fifty-seven thousand, three hundred twenty-nine".