644626 has 8 divisors (see below), whose sum is σ = 976140. Its totient is φ = 319248.

The previous prime is 644617. The next prime is 644629. The reversal of 644626 is 626446.

It can be written as a sum of positive squares in 2 ways, for example, as 641601 + 3025 = 801^2 + 55^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 644594 and 644603.

It is not an unprimeable number, because it can be changed into a prime (644629) by changing a digit.

644626 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1261 + ... + 1696.

2⁶⁴⁴⁶²⁶ is an apocalyptic number.

644626 is a deficient number, since it is larger than the sum of its proper divisors (331514).

644626 is a wasteful number, since it uses less digits than its factorization.

644626 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3068.

The product of its digits is 6912, while the sum is 28.

The square root of 644626 is about 802.8860442180. The cubic root of 644626 is about 86.3845229765.

The spelling of 644626 in words is "six hundred forty-four thousand, six hundred twenty-six".