644433250756 has 27 divisors (see below), whose sum is σ = 1134016022349. Its totient is φ = 320438498688.

The previous prime is 644433250753. The next prime is 644433250801. The reversal of 644433250756 is 657052334446.

The square root of 644433250756 is 802766.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 545072124100 + 99361126656 = 738290^2 + 315216^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644433250753) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 319499860 + ... + 319501876.

Almost surely, 2^644433250756 is an apocalyptic number.

644433250756 is the 802766-th square number.

It is an amenable number.

644433250756 is a deficient number, since it is larger than the sum of its proper divisors (489582771593).

644433250756 is an frugal number, since it uses more digits than its factorization.

644433250756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4436 (or 2218 counting only the distinct ones).

The product of its (nonzero) digits is 7257600, while the sum is 49.

Multiplying 644433250756 by its sum of digits (49), we get a square (31577229287044 = 5619362²).

The spelling of 644433250756 in words is "six hundred forty-four billion, four hundred thirty-three million, two hundred fifty thousand, seven hundred fifty-six".