644424581 has 2 divisors, whose sum is σ = 644424582. Its totient is φ = 644424580.

The previous prime is 644424551. The next prime is 644424629. The reversal of 644424581 is 185424446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 628304356 + 16120225 = 25066^2 + 4015^2 .

It is a cyclic number.

It is not a de Polignac number, because 644424581 - 2¹⁰ = 644423557 is a prime.

It is a super-2 number, since 2×644424581² = 830566081194051122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644424551) 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, 322212290 + 322212291.

It is an arithmetic number, because the mean of its divisors is an integer number (322212291).

Almost surely, 2^644424581 is an apocalyptic number.

It is an amenable number.

644424581 is a deficient number, since it is larger than the sum of its proper divisors (1).

644424581 is an equidigital number, since it uses as much as digits as its factorization.

644424581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 122880, while the sum is 38.

The square root of 644424581 is about 25385.5191201598. The cubic root of 644424581 is about 863.7552484073.

The spelling of 644424581 in words is "six hundred forty-four million, four hundred twenty-four thousand, five hundred eighty-one".