644334816 has 48 divisors (see below), whose sum is σ = 1790876304. Its totient is φ = 202143744.

The previous prime is 644334763. The next prime is 644334829. The reversal of 644334816 is 618433446.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (48).

It is a nude number because it is divisible by every one of its digits.

It is a congruent 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, 195775 + ... + 199038.

It is an arithmetic number, because the mean of its divisors is an integer number (37309923).

Almost surely, 2^644334816 is an apocalyptic number.

It is an amenable number.

644334816 is an abundant number, since it is smaller than the sum of its proper divisors (1146541488).

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

644334816 is a wasteful number, since it uses less digits than its factorization.

644334816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 394843 (or 394835 counting only the distinct ones).

The product of its digits is 165888, while the sum is 39.

The square root of 644334816 is about 25383.7510230462. The cubic root of 644334816 is about 863.7151410037.

The spelling of 644334816 in words is "six hundred forty-four million, three hundred thirty-four thousand, eight hundred sixteen".