644729 has 2 divisors, whose sum is σ = 644730. Its totient is φ = 644728.

The previous prime is 644717. The next prime is 644731. The reversal of 644729 is 927446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 462400 + 182329 = 680^2 + 427^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644729 is a prime.

It is a Sophie Germain prime.

Together with 644731, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 644695 and 644704.

It is not a weakly prime, because it can be changed into another prime (644789) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322364 + 322365.

It is an arithmetic number, because the mean of its divisors is an integer number (322365).

2⁶⁴⁴⁷²⁹ is an apocalyptic number.

It is an amenable number.

644729 is a deficient number, since it is larger than the sum of its proper divisors (1).

644729 is an equidigital number, since it uses as much as digits as its factorization.

644729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 32.

The square root of 644729 is about 802.9501852544. The cubic root of 644729 is about 86.3891236452.

The spelling of 644729 in words is "six hundred forty-four thousand, seven hundred twenty-nine".