644403605 has 16 divisors (see below), whose sum is σ = 803139840. Its totient is φ = 495991872.

The previous prime is 644403559. The next prime is 644403701. The reversal of 644403605 is 506304446.

It is a cyclic number.

It is not a de Polignac number, because 644403605 - 2¹⁰ = 644402581 is a prime.

It is a super-2 number, since 2×644403605² = 830512012273992050, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9374 + ... + 37103.

It is an arithmetic number, because the mean of its divisors is an integer number (50196240).

Almost surely, 2^644403605 is an apocalyptic number.

It is an amenable number.

644403605 is a deficient number, since it is larger than the sum of its proper divisors (158736235).

644403605 is a wasteful number, since it uses less digits than its factorization.

644403605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46588.

The product of its (nonzero) digits is 34560, while the sum is 32.

The square root of 644403605 is about 25385.1059678702. The cubic root of 644403605 is about 863.7458765702.

The spelling of 644403605 in words is "six hundred forty-four million, four hundred three thousand, six hundred five".