644969016 has 96 divisors (see below), whose sum is σ = 1781123760. Its totient is φ = 210802176.

The previous prime is 644969009. The next prime is 644969029. The reversal of 644969016 is 610969446.

644969016 is a `hidden beast` number, since 64 + 496 + 90 + 16 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1455691 + ... + 1456133.

Almost surely, 2^644969016 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 644969016, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (890561880).

644969016 is an abundant number, since it is smaller than the sum of its proper divisors (1136154744).

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

644969016 is a wasteful number, since it uses less digits than its factorization.

644969016 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 805 (or 798 counting only the distinct ones).

The product of its (nonzero) digits is 279936, while the sum is 45.

The square root of 644969016 is about 25396.2401941705. The cubic root of 644969016 is about 863.9984246370.

The spelling of 644969016 in words is "six hundred forty-four million, nine hundred sixty-nine thousand, sixteen".