644402626 has 12 divisors (see below), whose sum is σ = 1124416998. Its totient is φ = 276172512.

The previous prime is 644402623. The next prime is 644402713. The reversal of 644402626 is 626204446.

It can be written as a sum of positive squares in only one way, i.e., 637512001 + 6890625 = 25249^2 + 2625^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644402591 and 644402600.

It is not an unprimeable number, because it can be changed into a prime (644402623) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3287671 + ... + 3287866.

Almost surely, 2^644402626 is an apocalyptic number.

644402626 is a deficient number, since it is larger than the sum of its proper divisors (480014372).

644402626 is a wasteful number, since it uses less digits than its factorization.

644402626 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6575553 (or 6575546 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 34.

The square root of 644402626 is about 25385.0866849022. The cubic root of 644402626 is about 863.7454391592.

The spelling of 644402626 in words is "six hundred forty-four million, four hundred two thousand, six hundred twenty-six".