644043312 has 270 divisors, whose sum is σ = 2111586204. Its totient is φ = 189889920.

The previous prime is 644043311. The next prime is 644043391. The reversal of 644043312 is 213340446.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

644043312 is a `hidden beast` number, since 644 + 0 + 4 + 3 + 3 + 12 = 666.

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 (644043311) by changing a digit.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 17406558 + ... + 17406594.

Almost surely, 2^644043312 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 644043312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1055793102).

644043312 is an abundant number, since it is smaller than the sum of its proper divisors (1467542892).

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

644043312 is a wasteful number, since it uses less digits than its factorization.

644043312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119 (or 53 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 27.

The square root of 644043312 is about 25378.0084324992. The cubic root of 644043312 is about 863.5848700170.

Multiplying 644043312 by its sum of digits (27), we get a square (17389169424 = 131868²).

644043312 divided by its sum of digits (27) gives a square (23853456 = 4884²).

Multiplying 644043312 by its product of nonzero digits (6912), we get a square (4451627372544 = 2109888²).

Adding to 644043312 its reverse (213340446), we get a palindrome (857383758).

The spelling of 644043312 in words is "six hundred forty-four million, forty-three thousand, three hundred twelve".