644213 has 4 divisors (see below), whose sum is σ = 650028. Its totient is φ = 638400.

The previous prime is 644201. The next prime is 644227. The reversal of 644213 is 312446.

It is a happy number.

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 237169 + 407044 = 487^2 + 638^2 .

It is a cyclic number.

It is not a de Polignac number, because 644213 - 2⁴ = 644197 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 (644513) 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, 2738 + ... + 2963.

It is an arithmetic number, because the mean of its divisors is an integer number (162507).

2⁶⁴⁴²¹³ is an apocalyptic number.

It is an amenable number.

644213 is a deficient number, since it is larger than the sum of its proper divisors (5815).

644213 is a wasteful number, since it uses less digits than its factorization.

644213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5814.

The product of its digits is 576, while the sum is 20.

The square root of 644213 is about 802.6288058623. The cubic root of 644213 is about 86.3660707112.

Adding to 644213 its reverse (312446), we get a palindrome (956659).

The spelling of 644213 in words is "six hundred forty-four thousand, two hundred thirteen".