644704506 has 12 divisors (see below), whose sum is σ = 1396859802. Its totient is φ = 214901496.

The previous prime is 644704493. The next prime is 644704517. The reversal of 644704506 is 605407446.

644704506 is a `hidden beast` number, since 644 + 7 + 0 + 4 + 5 + 0 + 6 = 666.

It can be written as a sum of positive squares in only one way, i.e., 643078881 + 1625625 = 25359^2 + 1275^2 .

It is an unprimeable number.

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 in 5 ways as a sum of consecutive naturals, for example, 17908441 + ... + 17908476.

Almost surely, 2^644704506 is an apocalyptic number.

644704506 is an abundant number, since it is smaller than the sum of its proper divisors (752155296).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644704506 is a wasteful number, since it uses less digits than its factorization.

644704506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35816925 (or 35816922 counting only the distinct ones).

The product of its (nonzero) digits is 80640, while the sum is 36.

The square root of 644704506 is about 25391.0319995072. The cubic root of 644704506 is about 863.8802962378.

The spelling of 644704506 in words is "six hundred forty-four million, seven hundred four thousand, five hundred six".