644375784 has 64 divisors (see below), whose sum is σ = 1738376640. Its totient is φ = 197867520.

The previous prime is 644375779. The next prime is 644375789. The reversal of 644375784 is 487573446.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (644375779) and next prime (644375789).

It is a super-2 number, since 2×644375784² = 830440302011229312, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644375789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 176344 + ... + 179960.

It is an arithmetic number, because the mean of its divisors is an integer number (27162135).

Almost surely, 2^644375784 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 644375784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (869188320).

644375784 is an abundant number, since it is smaller than the sum of its proper divisors (1094000856).

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

644375784 is a wasteful number, since it uses less digits than its factorization.

644375784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4210 (or 4206 counting only the distinct ones).

The product of its digits is 2257920, while the sum is 48.

The square root of 644375784 is about 25384.5579831519. The cubic root of 644375784 is about 863.7334461515.

The spelling of 644375784 in words is "six hundred forty-four million, three hundred seventy-five thousand, seven hundred eighty-four".