644073637 has 8 divisors (see below), whose sum is σ = 650151000. Its totient is φ = 638023680.

The previous prime is 644073631. The next prime is 644073641. The reversal of 644073637 is 736370446.

It can be written as a sum of positive squares in 4 ways, for example, as 203661441 + 440412196 = 14271^2 + 20986^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644073637 - 2³ = 644073629 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 644073637.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644073631) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41989 + ... + 55237.

It is an arithmetic number, because the mean of its divisors is an integer number (81268875).

Almost surely, 2^644073637 is an apocalyptic number.

It is an amenable number.

644073637 is a deficient number, since it is larger than the sum of its proper divisors (6077363).

644073637 is a wasteful number, since it uses less digits than its factorization.

644073637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13703.

The product of its (nonzero) digits is 254016, while the sum is 40.

The square root of 644073637 is about 25378.6058915773. The cubic root of 644073637 is about 863.5984238674.

The spelling of 644073637 in words is "six hundred forty-four million, seventy-three thousand, six hundred thirty-seven".