644221 has 8 divisors (see below), whose sum is σ = 669600. Its totient is φ = 619440.

The previous prime is 644201. The next prime is 644227. The reversal of 644221 is 122446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644221 - 2¹⁵ = 611453 is a prime.

It is a Duffinian number.

644221 is a lucky number.

It is a plaindrome in base 14.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3510 + ... + 3688.

It is an arithmetic number, because the mean of its divisors is an integer number (83700).

2⁶⁴⁴²²¹ is an apocalyptic number.

644221 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

644221 is a deficient number, since it is larger than the sum of its proper divisors (25379).

644221 is a wasteful number, since it uses less digits than its factorization.

644221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 299.

The product of its digits is 384, while the sum is 19.

The square root of 644221 is about 802.6337894706. The cubic root of 644221 is about 86.3664282150.

Adding to 644221 its reverse (122446), we get a palindrome (766667).

The spelling of 644221 in words is "six hundred forty-four thousand, two hundred twenty-one".