81974279 has 2 divisors, whose sum is σ = 81974280. Its totient is φ = 81974278.

The previous prime is 81974209. The next prime is 81974281. The reversal of 81974279 is 97247918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81974279 - 2⁸ = 81974023 is a prime.

It is a Sophie Germain prime.

Together with 81974281, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_4777985 and since 81974279 and 4777985 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81974209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40987139 + 40987140.

It is an arithmetic number, because the mean of its divisors is an integer number (40987140).

Almost surely, 2^81974279 is an apocalyptic number.

81974279 is a deficient number, since it is larger than the sum of its proper divisors (1).

81974279 is an equidigital number, since it uses as much as digits as its factorization.

81974279 is an evil number, because the sum of its binary digits is even.

The product of its digits is 254016, while the sum is 47.

The square root of 81974279 is about 9053.9648221097. The cubic root of 81974279 is about 434.4027192704.

The spelling of 81974279 in words is "eighty-one million, nine hundred seventy-four thousand, two hundred seventy-nine".