644520240 has 400 divisors, whose sum is σ = 2757615168. Its totient is φ = 135862272.

The previous prime is 644520203. The next prime is 644520241. The reversal of 644520240 is 42025446.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (644520241) 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 79 ways as a sum of consecutive naturals, for example, 589134 + ... + 590226.

Almost surely, 2^644520240 is an apocalyptic number.

644520240 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 644520240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1378807584).

644520240 is an abundant number, since it is smaller than the sum of its proper divisors (2113094928).

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

644520240 is a wasteful number, since it uses less digits than its factorization.

644520240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1138 (or 1123 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 27.

The square root of 644520240 is about 25387.4031755908. The cubic root of 644520240 is about 863.7979851773.

Adding to 644520240 its reverse (42025446), we get a palindrome (686545686).

The spelling of 644520240 in words is "six hundred forty-four million, five hundred twenty thousand, two hundred forty".