644681459 has 2 divisors, whose sum is σ = 644681460. Its totient is φ = 644681458.

The previous prime is 644681449. The next prime is 644681461. The reversal of 644681459 is 954186446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644681459 - 2⁸ = 644681203 is a prime.

It is a super-2 number, since 2×644681459² = 831228367156737362, which contains 22 as substring.

Together with 644681461, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644681449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322340729 + 322340730.

It is an arithmetic number, because the mean of its divisors is an integer number (322340730).

Almost surely, 2^644681459 is an apocalyptic number.

644681459 is a deficient number, since it is larger than the sum of its proper divisors (1).

644681459 is an equidigital number, since it uses as much as digits as its factorization.

644681459 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 829440, while the sum is 47.

The square root of 644681459 is about 25390.5781541106. The cubic root of 644681459 is about 863.8700020714.

The spelling of 644681459 in words is "six hundred forty-four million, six hundred eighty-one thousand, four hundred fifty-nine".