644721149 has 2 divisors, whose sum is σ = 644721150. Its totient is φ = 644721148.

The previous prime is 644721113. The next prime is 644721163. The reversal of 644721149 is 941127446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 530380900 + 114340249 = 23030^2 + 10693^2 .

It is a cyclic number.

It is not a de Polignac number, because 644721149 - 2¹² = 644717053 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644720149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322360574 + 322360575.

It is an arithmetic number, because the mean of its divisors is an integer number (322360575).

Almost surely, 2^644721149 is an apocalyptic number.

It is an amenable number.

644721149 is a deficient number, since it is larger than the sum of its proper divisors (1).

644721149 is an equidigital number, since it uses as much as digits as its factorization.

644721149 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 38.

The square root of 644721149 is about 25391.3597312157. The cubic root of 644721149 is about 863.8877298429.

The spelling of 644721149 in words is "six hundred forty-four million, seven hundred twenty-one thousand, one hundred forty-nine".