644641 has 4 divisors (see below), whose sum is σ = 666900. Its totient is φ = 622384.

The previous prime is 644629. The next prime is 644647. The reversal of 644641 is 146446.

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 254016 + 390625 = 504^2 + 625^2 .

It is a cyclic number.

It is not a de Polignac number, because 644641 - 2⁷ = 644513 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644647) 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, 11086 + ... + 11143.

It is an arithmetic number, because the mean of its divisors is an integer number (166725).

2⁶⁴⁴⁶⁴¹ is an apocalyptic number.

It is an amenable number.

644641 is a deficient number, since it is larger than the sum of its proper divisors (22259).

644641 is a wasteful number, since it uses less digits than its factorization.

644641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22258.

The product of its digits is 2304, while the sum is 25.

The square root of 644641 is about 802.8953854644. The cubic root of 644641 is about 86.3851930073.

The spelling of 644641 in words is "six hundred forty-four thousand, six hundred forty-one".