644663236 has 48 divisors (see below), whose sum is σ = 1363855360. Its totient is φ = 260457120.

The previous prime is 644663231. The next prime is 644663249. The reversal of 644663236 is 632366446.

644663236 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (644663231) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 109381 + ... + 115123.

Almost surely, 2^644663236 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644663236, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (681927680).

644663236 is an abundant number, since it is smaller than the sum of its proper divisors (719192124).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644663236 is a wasteful number, since it uses less digits than its factorization.

644663236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5984 (or 5982 counting only the distinct ones).

The product of its digits is 373248, while the sum is 40.

The square root of 644663236 is about 25390.2192979895. The cubic root of 644663236 is about 863.8618624177.

The spelling of 644663236 in words is "six hundred forty-four million, six hundred sixty-three thousand, two hundred thirty-six".