644983551 has 12 divisors (see below), whose sum is σ = 961696320. Its totient is φ = 416118240.

The previous prime is 644983541. The next prime is 644983579. The reversal of 644983551 is 155389446.

644983551 is a `hidden beast` number, since 6 + 4 + 4 + 98 + 3 + 551 = 666.

It is not a de Polignac number, because 644983551 - 2⁹ = 644983039 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644983497 and 644983506.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644983501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1155606 + ... + 1156163.

It is an arithmetic number, because the mean of its divisors is an integer number (80141360).

Almost surely, 2^644983551 is an apocalyptic number.

644983551 is a deficient number, since it is larger than the sum of its proper divisors (316712769).

644983551 is a wasteful number, since it uses less digits than its factorization.

644983551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2311806 (or 2311803 counting only the distinct ones).

The product of its digits is 518400, while the sum is 45.

The square root of 644983551 is about 25396.5263569646. The cubic root of 644983551 is about 864.0049149347.

It can be divided in two parts, 6449 and 83551, that added together give a square (90000 = 300²).

The spelling of 644983551 in words is "six hundred forty-four million, nine hundred eighty-three thousand, five hundred fifty-one".