644438550 has 192 divisors, whose sum is σ = 1962731520. Its totient is φ = 136581120.

The previous prime is 644438539. The next prime is 644438563. The reversal of 644438550 is 55834446.

It is a super-2 number, since 2×644438550² = 830602089452205000, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644438499 and 644438508.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1409922 + ... + 1410378.

It is an arithmetic number, because the mean of its divisors is an integer number (10222560).

Almost surely, 2^644438550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644438550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (981365760).

644438550 is an abundant number, since it is smaller than the sum of its proper divisors (1318292970).

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

644438550 is a wasteful number, since it uses less digits than its factorization.

644438550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 575 (or 570 counting only the distinct ones).

The product of its (nonzero) digits is 230400, while the sum is 39.

The square root of 644438550 is about 25385.7942558432. The cubic root of 644438550 is about 863.7614894841.

The spelling of 644438550 in words is "six hundred forty-four million, four hundred thirty-eight thousand, five hundred fifty".