644129 has 2 divisors, whose sum is σ = 644130. Its totient is φ = 644128.

The previous prime is 644123. The next prime is 644131. The reversal of 644129 is 921446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 528529 + 115600 = 727^2 + 340^2 .

It is a cyclic number.

It is not a de Polignac number, because 644129 - 2⁸ = 643873 is a prime.

Together with 644131, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 644098 and 644107.

It is not a weakly prime, because it can be changed into another prime (644123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322064 + 322065.

It is an arithmetic number, because the mean of its divisors is an integer number (322065).

2⁶⁴⁴¹²⁹ is an apocalyptic number.

It is an amenable number.

644129 is a deficient number, since it is larger than the sum of its proper divisors (1).

644129 is an equidigital number, since it uses as much as digits as its factorization.

644129 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 26.

The square root of 644129 is about 802.5764761068. The cubic root of 644129 is about 86.3623167430.

The spelling of 644129 in words is "six hundred forty-four thousand, one hundred twenty-nine".