644218 has 4 divisors (see below), whose sum is σ = 966330. Its totient is φ = 322108.

The previous prime is 644201. The next prime is 644227. The reversal of 644218 is 812446.

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

It can be written as a sum of positive squares in only one way, i.e., 537289 + 106929 = 733^2 + 327^2 .

It is a junction number, because it is equal to n+sod(n) for n = 644192 and 644201.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 161053 + ... + 161056.

2⁶⁴⁴²¹⁸ is an apocalyptic number.

644218 is a deficient number, since it is larger than the sum of its proper divisors (322112).

644218 is a wasteful number, since it uses less digits than its factorization.

644218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322111.

The product of its digits is 1536, while the sum is 25.

The square root of 644218 is about 802.6319206212. The cubic root of 644218 is about 86.3662941514.

The spelling of 644218 in words is "six hundred forty-four thousand, two hundred eighteen".