644601321 has 135 divisors (see below), whose sum is σ = 1253315943. Its totient is φ = 329041440.

The previous prime is 644601283. The next prime is 644601341. The reversal of 644601321 is 123106446.

The square root of 644601321 is 25389.

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

644601321 is a `hidden beast` number, since 644 + 6 + 0 + 13 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 95355225 + 549246096 = 9765^2 + 23436^2 .

It is not a de Polignac number, because 644601321 - 2⁹ = 644600809 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (644601341) by changing a digit.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 20793576 + ... + 20793606.

Almost surely, 2^644601321 is an apocalyptic number.

644601321 is the 25389-th square number.

644601321 is the 12695-th centered octagonal number.

It is an amenable number.

644601321 is a deficient number, since it is larger than the sum of its proper divisors (608714622).

644601321 is a wasteful number, since it uses less digits than its factorization.

644601321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114 (or 54 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The cubic root of 644601321 is about 863.8342057454.

Adding to 644601321 its reverse (123106446), we get a palindrome (767707767).

The spelling of 644601321 in words is "six hundred forty-four million, six hundred one thousand, three hundred twenty-one".