644257 has 2 divisors, whose sum is σ = 644258. Its totient is φ = 644256.

The previous prime is 644239. The next prime is 644261. The reversal of 644257 is 752446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 331776 + 312481 = 576^2 + 559^2 .

It is a cyclic number.

It is not a de Polignac number, because 644257 - 2⁷ = 644129 is a prime.

It is not a weakly prime, because it can be changed into another prime (644227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322128 + 322129.

It is an arithmetic number, because the mean of its divisors is an integer number (322129).

2⁶⁴⁴²⁵⁷ is an apocalyptic number.

It is an amenable number.

644257 is a deficient number, since it is larger than the sum of its proper divisors (1).

644257 is an equidigital number, since it uses as much as digits as its factorization.

644257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6720, while the sum is 28.

The square root of 644257 is about 802.6562153251. The cubic root of 644257 is about 86.3680369452.

The spelling of 644257 in words is "six hundred forty-four thousand, two hundred fifty-seven".