644121743 has 12 divisors (see below), whose sum is σ = 655765344. Its totient is φ = 632664000.

The previous prime is 644121701. The next prime is 644121763. The reversal of 644121743 is 347121446.

It is not a de Polignac number, because 644121743 - 2¹² = 644117647 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644121763) 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 11 ways as a sum of consecutive naturals, for example, 2376698 + ... + 2376968.

It is an arithmetic number, because the mean of its divisors is an integer number (54647112).

Almost surely, 2^644121743 is an apocalyptic number.

644121743 is a deficient number, since it is larger than the sum of its proper divisors (11643601).

644121743 is a wasteful number, since it uses less digits than its factorization.

644121743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 706 (or 605 counting only the distinct ones).

The product of its digits is 16128, while the sum is 32.

The square root of 644121743 is about 25379.5536406770. The cubic root of 644121743 is about 863.6199241169.

The spelling of 644121743 in words is "six hundred forty-four million, one hundred twenty-one thousand, seven hundred forty-three".