644116656 has 80 divisors (see below), whose sum is σ = 1745888256. Its totient is φ = 204238848.

The previous prime is 644116639. The next prime is 644116661. The reversal of 644116656 is 656611446.

It is a happy number.

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, 211561 + ... + 214583.

Almost surely, 2^644116656 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 644116656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (872944128).

644116656 is an abundant number, since it is smaller than the sum of its proper divisors (1101771600).

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

644116656 is a wasteful number, since it uses less digits than its factorization.

644116656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3250 (or 3244 counting only the distinct ones).

The product of its digits is 103680, while the sum is 39.

The square root of 644116656 is about 25379.4534220105. The cubic root of 644116656 is about 863.6176506097.

The spelling of 644116656 in words is "six hundred forty-four million, one hundred sixteen thousand, six hundred fifty-six".