644405748 has 96 divisors (see below), whose sum is σ = 1833968640. Its totient is φ = 172005120.

The previous prime is 644405737. The next prime is 644405759. The reversal of 644405748 is 847504446.

It is an interprime number because it is at equal distance from previous prime (644405737) and next prime (644405759).

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 113743 + ... + 119273.

It is an arithmetic number, because the mean of its divisors is an integer number (19103840).

Almost surely, 2^644405748 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 644405748, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (916984320).

644405748 is an abundant number, since it is smaller than the sum of its proper divisors (1189562892).

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

644405748 is a wasteful number, since it uses less digits than its factorization.

644405748 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5637 (or 5635 counting only the distinct ones).

The product of its (nonzero) digits is 430080, while the sum is 42.

The square root of 644405748 is about 25385.1481776254. The cubic root of 644405748 is about 863.7468340474.

The spelling of 644405748 in words is "six hundred forty-four million, four hundred five thousand, seven hundred forty-eight".