81806579 has 2 divisors, whose sum is σ = 81806580. Its totient is φ = 81806578.

The previous prime is 81806573. The next prime is 81806611. The reversal of 81806579 is 97560818.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81806579 - 2⁴ = 81806563 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81806573) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40903289 + 40903290.

It is an arithmetic number, because the mean of its divisors is an integer number (40903290).

Almost surely, 2^81806579 is an apocalyptic number.

81806579 is a deficient number, since it is larger than the sum of its proper divisors (1).

81806579 is an equidigital number, since it uses as much as digits as its factorization.

81806579 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120960, while the sum is 44.

The square root of 81806579 is about 9044.6989446858. The cubic root of 81806579 is about 434.1062886055.

The spelling of 81806579 in words is "eighty-one million, eight hundred six thousand, five hundred seventy-nine".