644121 has 6 divisors (see below), whose sum is σ = 930410. Its totient is φ = 429408.

The previous prime is 644117. The next prime is 644123. The reversal of 644121 is 121446.

644121 is a `hidden beast` number, since 644 + 1 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 608400 + 35721 = 780^2 + 189^2 .

It is not a de Polignac number, because 644121 - 2² = 644117 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644094 and 644103.

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 5 ways as a sum of consecutive naturals, for example, 35776 + ... + 35793.

2⁶⁴⁴¹²¹ is an apocalyptic number.

It is an amenable number.

644121 is a deficient number, since it is larger than the sum of its proper divisors (286289).

644121 is a wasteful number, since it uses less digits than its factorization.

644121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71575 (or 71572 counting only the distinct ones).

The product of its digits is 192, while the sum is 18.

The square root of 644121 is about 802.5714921426. The cubic root of 644121 is about 86.3619592052.

Adding to 644121 its reverse (121446), we get a palindrome (765567).

The spelling of 644121 in words is "six hundred forty-four thousand, one hundred twenty-one".