644192881 has 2 divisors, whose sum is σ = 644192882. Its totient is φ = 644192880.

The previous prime is 644192867. The next prime is 644192909. The reversal of 644192881 is 188291446.

644192881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 622253025 + 21939856 = 24945^2 + 4684^2 .

It is a cyclic number.

It is not a de Polignac number, because 644192881 - 2¹⁵ = 644160113 is a prime.

It is a super-2 number, since 2×644192881² = 829968935862160322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (644192851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322096440 + 322096441.

It is an arithmetic number, because the mean of its divisors is an integer number (322096441).

Almost surely, 2^644192881 is an apocalyptic number.

It is an amenable number.

644192881 is a deficient number, since it is larger than the sum of its proper divisors (1).

644192881 is an equidigital number, since it uses as much as digits as its factorization.

644192881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 110592, while the sum is 43.

The square root of 644192881 is about 25380.9550844723. The cubic root of 644192881 is about 863.6517162086.

The spelling of 644192881 in words is "six hundred forty-four million, one hundred ninety-two thousand, eight hundred eighty-one".