644721152 has 40 divisors (see below), whose sum is σ = 1323037716. Its totient is φ = 313638912.

The previous prime is 644721149. The next prime is 644721163. The reversal of 644721152 is 251127446.

It can be written as a sum of positive squares in 2 ways, for example, as 575232256 + 69488896 = 23984^2 + 8336^2 .

It is a Harshad number since it is a multiple of its sum of digits (32).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1928 + ... + 35960.

Almost surely, 2^644721152 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 644721152, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (661518858).

644721152 is an abundant number, since it is smaller than the sum of its proper divisors (678316564).

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

644721152 is an equidigital number, since it uses as much as digits as its factorization.

644721152 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34088 (or 34072 counting only the distinct ones).

The product of its digits is 13440, while the sum is 32.

The square root of 644721152 is about 25391.3597902909. The cubic root of 644721152 is about 863.8877311828.

Adding to 644721152 its reverse (251127446), we get a palindrome (895848598).

The spelling of 644721152 in words is "six hundred forty-four million, seven hundred twenty-one thousand, one hundred fifty-two".