644216990 has 16 divisors (see below), whose sum is σ = 1190931552. Its totient is φ = 250722144.

The previous prime is 644216987. The next prime is 644217011. The reversal of 644216990 is 99612446.

644216990 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 870194 + ... + 870933.

It is an arithmetic number, because the mean of its divisors is an integer number (74433222).

Almost surely, 2^644216990 is an apocalyptic number.

644216990 is a deficient number, since it is larger than the sum of its proper divisors (546714562).

644216990 is a wasteful number, since it uses less digits than its factorization.

644216990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1741171.

The product of its (nonzero) digits is 93312, while the sum is 41.

The square root of 644216990 is about 25381.4300227548. The cubic root of 644216990 is about 863.6624901657.

It can be divided in two parts, 6442 and 16990, that added together give a palindrome (23432).

The spelling of 644216990 in words is "six hundred forty-four million, two hundred sixteen thousand, nine hundred ninety".