644926 has 4 divisors (see below), whose sum is σ = 967392. Its totient is φ = 322462.

The previous prime is 644923. The next prime is 644933. The reversal of 644926 is 629446.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 629446 = 2 ⋅314723.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644923) 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 as a sum of consecutive naturals, namely, 161230 + ... + 161233.

It is an arithmetic number, because the mean of its divisors is an integer number (241848).

2⁶⁴⁴⁹²⁶ is an apocalyptic number.

644926 is a deficient number, since it is larger than the sum of its proper divisors (322466).

644926 is a wasteful number, since it uses less digits than its factorization.

644926 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322465.

The product of its digits is 10368, while the sum is 31.

The square root of 644926 is about 803.0728485013. The cubic root of 644926 is about 86.3979216178.

The spelling of 644926 in words is "six hundred forty-four thousand, nine hundred twenty-six".