81563971 has 2 divisors, whose sum is σ = 81563972. Its totient is φ = 81563970.

The previous prime is 81563939. The next prime is 81563981. The reversal of 81563971 is 17936518.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81563971 - 2⁵ = 81563939 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81563981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40781985 + 40781986.

It is an arithmetic number, because the mean of its divisors is an integer number (40781986).

Almost surely, 2^81563971 is an apocalyptic number.

81563971 is a deficient number, since it is larger than the sum of its proper divisors (1).

81563971 is an equidigital number, since it uses as much as digits as its factorization.

81563971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 45360, while the sum is 40.

The square root of 81563971 is about 9031.2773736609. The cubic root of 81563971 is about 433.6767308908.

The spelling of 81563971 in words is "eighty-one million, five hundred sixty-three thousand, nine hundred seventy-one".