644418 has 12 divisors (see below), whose sum is σ = 1396278. Its totient is φ = 214800.

The previous prime is 644411. The next prime is 644431. The reversal of 644418 is 814446.

644418 is a `hidden beast` number, since 644 + 4 + 18 = 666.

It can be written as a sum of positive squares in only one way, i.e., 613089 + 31329 = 783^2 + 177^2 .

It is an Ulam number.

It is a plaindrome in base 14.

It is a junction number, because it is equal to n+sod(n) for n = 644391 and 644400.

It is not an unprimeable number, because it can be changed into a prime (644411) by changing a digit.

644418 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 17883 + ... + 17918.

2⁶⁴⁴⁴¹⁸ is an apocalyptic number.

644418 is an abundant number, since it is smaller than the sum of its proper divisors (751860).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644418 is a wasteful number, since it uses less digits than its factorization.

644418 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35809 (or 35806 counting only the distinct ones).

The product of its digits is 3072, while the sum is 27.

The square root of 644418 is about 802.7565010637. The cubic root of 644418 is about 86.3752308114.

The spelling of 644418 in words is "six hundred forty-four thousand, four hundred eighteen".