644723712 has 132 divisors (see below), whose sum is σ = 1931319936. Its totient is φ = 214824960.

The previous prime is 644723711. The next prime is 644723731. The reversal of 644723712 is 217327446.

644723712 is a `hidden beast` number, since 644 + 7 + 2 + 3 + 7 + 1 + 2 = 666.

It is a super-3 number, since 3×644723712³ (a number of 27 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644723711) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 247537 + ... + 250127.

Almost surely, 2^644723712 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 644723712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (965659968).

644723712 is an abundant number, since it is smaller than the sum of its proper divisors (1286596224).

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

644723712 is an equidigital number, since it uses as much as digits as its factorization.

644723712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2626 (or 2596 counting only the distinct ones).

The product of its digits is 56448, while the sum is 36.

The square root of 644723712 is about 25391.4102010897. The cubic root of 644723712 is about 863.8888745968. Note that the first 4 decimals are identical.

The spelling of 644723712 in words is "six hundred forty-four million, seven hundred twenty-three thousand, seven hundred twelve".