81957977 has 2 divisors, whose sum is σ = 81957978. Its totient is φ = 81957976.

The previous prime is 81957971. The next prime is 81957979. The reversal of 81957977 is 77975918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 46185616 + 35772361 = 6796^2 + 5981^2 .

It is a cyclic number.

It is not a de Polignac number, because 81957977 - 2⁸ = 81957721 is a prime.

Together with 81957979, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81957971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40978988 + 40978989.

It is an arithmetic number, because the mean of its divisors is an integer number (40978989).

Almost surely, 2^81957977 is an apocalyptic number.

It is an amenable number.

81957977 is a deficient number, since it is larger than the sum of its proper divisors (1).

81957977 is an equidigital number, since it uses as much as digits as its factorization.

81957977 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1111320, while the sum is 53.

The square root of 81957977 is about 9053.0645087727. The cubic root of 81957977 is about 434.3739212022.

The spelling of 81957977 in words is "eighty-one million, nine hundred fifty-seven thousand, nine hundred seventy-seven".