644686395 has 16 divisors (see below), whose sum is σ = 1046895360. Its totient is φ = 338700384.

The previous prime is 644686381. The next prime is 644686423. The reversal of 644686395 is 593686446.

It is a happy number.

644686395 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644686395 - 2⁴ = 644686379 is a prime.

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, 319735 + ... + 321744.

It is an arithmetic number, because the mean of its divisors is an integer number (65430960).

Almost surely, 2^644686395 is an apocalyptic number.

644686395 is a deficient number, since it is larger than the sum of its proper divisors (402208965).

644686395 is a wasteful number, since it uses less digits than its factorization.

644686395 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 641554.

The product of its digits is 3732480, while the sum is 51.

The square root of 644686395 is about 25390.6753553347. The cubic root of 644686395 is about 863.8722068044.

Adding to 644686395 its sum of digits (51), we get a palindrome (644686446).

The spelling of 644686395 in words is "six hundred forty-four million, six hundred eighty-six thousand, three hundred ninety-five".