644657 has 8 divisors (see below), whose sum is σ = 735336. Its totient is φ = 559872.

The previous prime is 644653. The next prime is 644669. The reversal of 644657 is 756446.

644657 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 279841 + 364816 = 529^2 + 604^2 .

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 644657 - 2² = 644653 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644657.

It is not an unprimeable number, because it can be changed into a prime (644653) 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, 1238 + ... + 1679.

It is an arithmetic number, because the mean of its divisors is an integer number (91917).

2⁶⁴⁴⁶⁵⁷ is an apocalyptic number.

It is an amenable number.

644657 is a deficient number, since it is larger than the sum of its proper divisors (90679).

644657 is a wasteful number, since it uses less digits than its factorization.

644657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2947.

The product of its digits is 20160, while the sum is 32.

The square root of 644657 is about 802.9053493408. The cubic root of 644657 is about 86.3859076953.

The spelling of 644657 in words is "six hundred forty-four thousand, six hundred fifty-seven".