81971 has 2 divisors, whose sum is σ = 81972. Its totient is φ = 81970.

The previous prime is 81967. The next prime is 81973. The reversal of 81971 is 17918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81971 - 2² = 81967 is a prime.

Together with 81973, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81971.

It is not a weakly prime, because it can be changed into another prime (81973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40985 + 40986.

It is an arithmetic number, because the mean of its divisors is an integer number (40986).

2⁸¹⁹⁷¹ is an apocalyptic number.

81971 is a deficient number, since it is larger than the sum of its proper divisors (1).

81971 is an equidigital number, since it uses as much as digits as its factorization.

81971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 504, while the sum is 26.

The square root of 81971 is about 286.3057805913. The cubic root of 81971 is about 43.4396927106.

The spelling of 81971 in words is "eighty-one thousand, nine hundred seventy-one".