81643279 has 2 divisors, whose sum is σ = 81643280. Its totient is φ = 81643278.

The previous prime is 81643253. The next prime is 81643327. The reversal of 81643279 is 97234618.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81643279 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81643229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40821639 + 40821640.

It is an arithmetic number, because the mean of its divisors is an integer number (40821640).

Almost surely, 2^81643279 is an apocalyptic number.

81643279 is a deficient number, since it is larger than the sum of its proper divisors (1).

81643279 is an equidigital number, since it uses as much as digits as its factorization.

81643279 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 40.

The square root of 81643279 is about 9035.6670478720. The cubic root of 81643279 is about 433.8172459253.

The spelling of 81643279 in words is "eighty-one million, six hundred forty-three thousand, two hundred seventy-nine".