81646979 has 2 divisors, whose sum is σ = 81646980. Its totient is φ = 81646978.

The previous prime is 81646969. The next prime is 81646991. The reversal of 81646979 is 97964618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81646979 - 2²⁰ = 80598403 is a prime.

It is not a weakly prime, because it can be changed into another prime (81646969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40823489 + 40823490.

It is an arithmetic number, because the mean of its divisors is an integer number (40823490).

Almost surely, 2^81646979 is an apocalyptic number.

81646979 is a deficient number, since it is larger than the sum of its proper divisors (1).

81646979 is an equidigital number, since it uses as much as digits as its factorization.

81646979 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 653184, while the sum is 50.

The square root of 81646979 is about 9035.8717897057. The cubic root of 81646979 is about 433.8237992289.

The spelling of 81646979 in words is "eighty-one million, six hundred forty-six thousand, nine hundred seventy-nine".