644237616 has 40 divisors (see below), whose sum is σ = 1815580224. Its totient is φ = 195223360.

The previous prime is 644237603. The next prime is 644237651. The reversal of 644237616 is 616732446.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 609546 + ... + 610601.

Almost surely, 2^644237616 is an apocalyptic number.

644237616 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is an amenable number.

644237616 is an abundant number, since it is smaller than the sum of its proper divisors (1171342608).

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

644237616 is a wasteful number, since it uses less digits than its factorization.

644237616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1220169 (or 1220163 counting only the distinct ones).

The product of its digits is 145152, while the sum is 39.

The square root of 644237616 is about 25381.8363401863. The cubic root of 644237616 is about 863.6717074081.

The spelling of 644237616 in words is "six hundred forty-four million, two hundred thirty-seven thousand, six hundred sixteen".