644566340 has 48 divisors (see below), whose sum is σ = 1484892864. Its totient is φ = 233078400.

The previous prime is 644566333. The next prime is 644566343. The reversal of 644566340 is 43665446.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 644566294 and 644566303.

It is not an unprimeable number, because it can be changed into a prime (644566343) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31727 + ... + 47913.

It is an arithmetic number, because the mean of its divisors is an integer number (30935268).

Almost surely, 2^644566340 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 644566340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (742446432).

644566340 is an abundant number, since it is smaller than the sum of its proper divisors (840326524).

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

644566340 is a wasteful number, since it uses less digits than its factorization.

644566340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16388 (or 16386 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 38.

The square root of 644566340 is about 25388.3110899485. The cubic root of 644566340 is about 863.8185793781.

The spelling of 644566340 in words is "six hundred forty-four million, five hundred sixty-six thousand, three hundred forty".