644407 has 4 divisors (see below), whose sum is σ = 646416. Its totient is φ = 642400.

The previous prime is 644401. The next prime is 644411. The reversal of 644407 is 704446.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 644407 - 2¹¹ = 642359 is a prime.

It is a Duffinian number.

644407 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644401) 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, 403 + ... + 1204.

It is an arithmetic number, because the mean of its divisors is an integer number (161604).

2⁶⁴⁴⁴⁰⁷ is an apocalyptic number.

644407 is a deficient number, since it is larger than the sum of its proper divisors (2009).

644407 is a wasteful number, since it uses less digits than its factorization.

644407 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2008.

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 644407 is about 802.7496496418. The cubic root of 644407 is about 86.3747393431.

The spelling of 644407 in words is "six hundred forty-four thousand, four hundred seven".