644646406 has 8 divisors (see below), whose sum is σ = 969522120. Its totient is φ = 321472368.

The previous prime is 644646361. The next prime is 644646413. The reversal of 644646406 is 604646446.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 424471 + ... + 425986.

It is an arithmetic number, because the mean of its divisors is an integer number (121190265).

Almost surely, 2^644646406 is an apocalyptic number.

644646406 is a deficient number, since it is larger than the sum of its proper divisors (324875714).

644646406 is a wasteful number, since it uses less digits than its factorization.

644646406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 850838.

The product of its (nonzero) digits is 331776, while the sum is 40.

The square root of 644646406 is about 25389.8878689923. The cubic root of 644646406 is about 863.8543448381.

Adding to 644646406 its sum of digits (40), we get a palindrome (644646446).

The spelling of 644646406 in words is "six hundred forty-four million, six hundred forty-six thousand, four hundred six".