644961439 has 8 divisors (see below), whose sum is σ = 657710928. Its totient is φ = 632336640.

The previous prime is 644961437. The next prime is 644961481. The reversal of 644961439 is 934169446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644961439 - 2¹ = 644961437 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644961433) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20692 + ... + 41449.

It is an arithmetic number, because the mean of its divisors is an integer number (82213866).

Almost surely, 2^644961439 is an apocalyptic number.

644961439 is a deficient number, since it is larger than the sum of its proper divisors (12749489).

644961439 is a wasteful number, since it uses less digits than its factorization.

644961439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62345.

The product of its digits is 559872, while the sum is 46.

The square root of 644961439 is about 25396.0910181075. The cubic root of 644961439 is about 863.9950412488.

The spelling of 644961439 in words is "six hundred forty-four million, nine hundred sixty-one thousand, four hundred thirty-nine".