81664519 has 2 divisors, whose sum is σ = 81664520. Its totient is φ = 81664518.

The previous prime is 81664511. The next prime is 81664523. The reversal of 81664519 is 91546618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81664519 - 2³ = 81664511 is a prime.

It is a super-2 number, since 2×81664519² = 13338187327002722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81664511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40832259 + 40832260.

It is an arithmetic number, because the mean of its divisors is an integer number (40832260).

Almost surely, 2^81664519 is an apocalyptic number.

81664519 is a deficient number, since it is larger than the sum of its proper divisors (1).

81664519 is an equidigital number, since it uses as much as digits as its factorization.

81664519 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 51840, while the sum is 40.

The square root of 81664519 is about 9036.8423135518. The cubic root of 81664519 is about 433.8548627363.

The spelling of 81664519 in words is "eighty-one million, six hundred sixty-four thousand, five hundred nineteen".