81318779 has 2 divisors, whose sum is σ = 81318780. Its totient is φ = 81318778.

The previous prime is 81318709. The next prime is 81318781. The reversal of 81318779 is 97781318.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81318779 is a prime.

It is a super-2 number, since 2×81318779² = 13225487636101682, which contains 22 as substring.

Together with 81318781, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81318709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40659389 + 40659390.

It is an arithmetic number, because the mean of its divisors is an integer number (40659390).

Almost surely, 2^81318779 is an apocalyptic number.

81318779 is a deficient number, since it is larger than the sum of its proper divisors (1).

81318779 is an equidigital number, since it uses as much as digits as its factorization.

81318779 is an evil number, because the sum of its binary digits is even.

The product of its digits is 84672, while the sum is 44.

The square root of 81318779 is about 9017.6925540850. The cubic root of 81318779 is about 433.2417316569.

The spelling of 81318779 in words is "eighty-one million, three hundred eighteen thousand, seven hundred seventy-nine".