644398225 has 9 divisors (see below), whose sum is σ = 799211217. Its totient is φ = 515417040.

The previous prime is 644398217. The next prime is 644398231. The reversal of 644398225 is 522893446.

The square root of 644398225 is 25385.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 134722449 + 509675776 = 11607^2 + 22576^2 .

It is not a de Polignac number, because 644398225 - 2³ = 644398217 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 124387 + ... + 129463.

Almost surely, 2^644398225 is an apocalyptic number.

644398225 is the 25385-th square number.

644398225 is the 12693-rd centered octagonal number.

It is an amenable number.

644398225 is a deficient number, since it is larger than the sum of its proper divisors (154812992).

644398225 is an frugal number, since it uses more digits than its factorization.

644398225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10164 (or 5082 counting only the distinct ones).

The product of its digits is 414720, while the sum is 43.

The cubic root of 644398225 is about 863.7434728149.

The spelling of 644398225 in words is "six hundred forty-four million, three hundred ninety-eight thousand, two hundred twenty-five".