644451 has 4 divisors (see below), whose sum is σ = 859272. Its totient is φ = 429632.

The previous prime is 644447. The next prime is 644489. The reversal of 644451 is 154446.

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 644451 - 2² = 644447 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (644401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107406 + ... + 107411.

It is an arithmetic number, because the mean of its divisors is an integer number (214818).

2⁶⁴⁴⁴⁵¹ is an apocalyptic number.

644451 is a deficient number, since it is larger than the sum of its proper divisors (214821).

644451 is a wasteful number, since it uses less digits than its factorization.

644451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214820.

The product of its digits is 1920, while the sum is 24.

The square root of 644451 is about 802.7770549785. Note that the first 3 decimals coincide. The cubic root of 644451 is about 86.3767051825.

Adding to 644451 its reverse (154446), we get a palindrome (798897).

It can be divided in two parts, 64445 and 1, that added together give a palindrome (64446).

The spelling of 644451 in words is "six hundred forty-four thousand, four hundred fifty-one".