644005406 has 8 divisors (see below), whose sum is σ = 1053827064. Its totient is φ = 292729720.

The previous prime is 644005403. The next prime is 644005423. The reversal of 644005406 is 604500446.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644005403) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14636465 + ... + 14636508.

It is an arithmetic number, because the mean of its divisors is an integer number (131728383).

Almost surely, 2^644005406 is an apocalyptic number.

644005406 is a deficient number, since it is larger than the sum of its proper divisors (409821658).

644005406 is a wasteful number, since it uses less digits than its factorization.

644005406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29272986.

The product of its (nonzero) digits is 11520, while the sum is 29.

The square root of 644005406 is about 25377.2615937969. The cubic root of 644005406 is about 863.5679272174.

The spelling of 644005406 in words is "six hundred forty-four million, five thousand, four hundred six".