81568819 has 2 divisors, whose sum is σ = 81568820. Its totient is φ = 81568818.

The previous prime is 81568801. The next prime is 81568849. The reversal of 81568819 is 91886518.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81568819 - 2¹⁵ = 81536051 is a prime.

It is a super-2 number, since 2×81568819² = 13306944466109522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81568849) 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, 40784409 + 40784410.

It is an arithmetic number, because the mean of its divisors is an integer number (40784410).

Almost surely, 2^81568819 is an apocalyptic number.

81568819 is a deficient number, since it is larger than the sum of its proper divisors (1).

81568819 is an equidigital number, since it uses as much as digits as its factorization.

81568819 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 138240, while the sum is 46.

The square root of 81568819 is about 9031.5457702433. The cubic root of 81568819 is about 433.6853230143.

The spelling of 81568819 in words is "eighty-one million, five hundred sixty-eight thousand, eight hundred nineteen".