644341331 has 2 divisors, whose sum is σ = 644341332. Its totient is φ = 644341330.

The previous prime is 644341309. The next prime is 644341333. The reversal of 644341331 is 133143446.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644341331 is a prime.

It is a super-2 number, since 2×644341331² = 830351501669703122, which contains 22 as substring.

Together with 644341333, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 644341294 and 644341303.

It is not a weakly prime, because it can be changed into another prime (644341333) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322170665 + 322170666.

It is an arithmetic number, because the mean of its divisors is an integer number (322170666).

Almost surely, 2^644341331 is an apocalyptic number.

644341331 is a deficient number, since it is larger than the sum of its proper divisors (1).

644341331 is an equidigital number, since it uses as much as digits as its factorization.

644341331 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 29.

The square root of 644341331 is about 25383.8793528491. The cubic root of 644341331 is about 863.7180520602.

Adding to 644341331 its reverse (133143446), we get a palindrome (777484777).

It can be divided in two parts, 6443 and 41331, that added together give a palindrome (47774).

The spelling of 644341331 in words is "six hundred forty-four million, three hundred forty-one thousand, three hundred thirty-one".