644773740 has 192 divisors, whose sum is σ = 2067878400. Its totient is φ = 148801536.

The previous prime is 644773699. The next prime is 644773781. The reversal of 644773740 is 47377446.

It is an interprime number because it is at equal distance from previous prime (644773699) and next prime (644773781).

It is a junction number, because it is equal to n+sod(n) for n = 644773692 and 644773701.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2059824 + ... + 2060136.

It is an arithmetic number, because the mean of its divisors is an integer number (10770200).

Almost surely, 2^644773740 is an apocalyptic number.

644773740 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644773740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1033939200).

644773740 is an abundant number, since it is smaller than the sum of its proper divisors (1423104660).

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

644773740 is a wasteful number, since it uses less digits than its factorization.

644773740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 496 (or 494 counting only the distinct ones).

The product of its (nonzero) digits is 395136, while the sum is 42.

The square root of 644773740 is about 25392.3953182838. The cubic root of 644773740 is about 863.9112188010.

The spelling of 644773740 in words is "six hundred forty-four million, seven hundred seventy-three thousand, seven hundred forty".