644120 has 16 divisors (see below), whose sum is σ = 1449360. Its totient is φ = 257632.

The previous prime is 644117. The next prime is 644123. The reversal of 644120 is 21446.

It is an interprime number because it is at equal distance from previous prime (644117) and next prime (644123).

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644123) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8012 + ... + 8091.

It is an arithmetic number, because the mean of its divisors is an integer number (90585).

2⁶⁴⁴¹²⁰ is an apocalyptic number.

It is an amenable number.

644120 is an abundant number, since it is smaller than the sum of its proper divisors (805240).

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

644120 is a wasteful number, since it uses less digits than its factorization.

644120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16114 (or 16110 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 644120 is about 802.5708691449. The cubic root of 644120 is about 86.3619145128.

Adding to 644120 its reverse (21446), we get a palindrome (665566).

The spelling of 644120 in words is "six hundred forty-four thousand, one hundred twenty".