644393380 has 12 divisors (see below), whose sum is σ = 1353226140. Its totient is φ = 257757344.

The previous prime is 644393353. The next prime is 644393383. The reversal of 644393380 is 83393446.

It can be written as a sum of positive squares in 2 ways, for example, as 222666084 + 421727296 = 14922^2 + 20536^2 .

It is a super-5 number, since 5×644393380⁵ (a number of 45 digits) contains 55555 as substring.

It is not an unprimeable number, because it can be changed into a prime (644393383) 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 3 ways as a sum of consecutive naturals, for example, 16109815 + ... + 16109854.

It is an arithmetic number, because the mean of its divisors is an integer number (112768845).

Almost surely, 2^644393380 is an apocalyptic number.

It is an amenable number.

644393380 is an abundant number, since it is smaller than the sum of its proper divisors (708832760).

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

644393380 is a wasteful number, since it uses less digits than its factorization.

644393380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32219678 (or 32219676 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 40.

The square root of 644393380 is about 25384.9045694484. The cubic root of 644393380 is about 863.7413080833.

The spelling of 644393380 in words is "six hundred forty-four million, three hundred ninety-three thousand, three hundred eighty".