644969 has 4 divisors (see below), whose sum is σ = 694596. Its totient is φ = 595344.

The previous prime is 644951. The next prime is 644977. The reversal of 644969 is 969446.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 25600 + 619369 = 160^2 + 787^2 .

It is a cyclic number.

It is not a de Polignac number, because 644969 - 2¹² = 640873 is a prime.

It is a super-2 number, since 2×644969² = 831970021922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644909) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24794 + ... + 24819.

It is an arithmetic number, because the mean of its divisors is an integer number (173649).

2⁶⁴⁴⁹⁶⁹ is an apocalyptic number.

It is an amenable number.

644969 is a deficient number, since it is larger than the sum of its proper divisors (49627).

644969 is a wasteful number, since it uses less digits than its factorization.

644969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49626.

The product of its digits is 46656, while the sum is 38.

The square root of 644969 is about 803.0996202216. The cubic root of 644969 is about 86.3998417493.

The spelling of 644969 in words is "six hundred forty-four thousand, nine hundred sixty-nine".