644047 has 2 divisors, whose sum is σ = 644048. Its totient is φ = 644046.

The previous prime is 644029. The next prime is 644051. The reversal of 644047 is 740446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644047 - 2⁷ = 643919 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644057) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322023 + 322024.

It is an arithmetic number, because the mean of its divisors is an integer number (322024).

2⁶⁴⁴⁰⁴⁷ is an apocalyptic number.

644047 is a deficient number, since it is larger than the sum of its proper divisors (1).

644047 is an equidigital number, since it uses as much as digits as its factorization.

644047 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 644047 is about 802.5253890065. The cubic root of 644047 is about 86.3586518402.

The spelling of 644047 in words is "six hundred forty-four thousand, forty-seven".