644143321 has 2 divisors, whose sum is σ = 644143322. Its totient is φ = 644143320.

The previous prime is 644143307. The next prime is 644143351. The reversal of 644143321 is 123341446.

644143321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 432848025 + 211295296 = 20805^2 + 14536^2 .

It is a cyclic number.

It is not a de Polignac number, because 644143321 - 2⁷ = 644143193 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644143321.

It is not a weakly prime, because it can be changed into another prime (644143351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322071660 + 322071661.

It is an arithmetic number, because the mean of its divisors is an integer number (322071661).

Almost surely, 2^644143321 is an apocalyptic number.

It is an amenable number.

644143321 is a deficient number, since it is larger than the sum of its proper divisors (1).

644143321 is an equidigital number, since it uses as much as digits as its factorization.

644143321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6912, while the sum is 28.

The square root of 644143321 is about 25379.9787430959. The cubic root of 644143321 is about 863.6295677300.

Adding to 644143321 its reverse (123341446), we get a palindrome (767484767).

The spelling of 644143321 in words is "six hundred forty-four million, one hundred forty-three thousand, three hundred twenty-one".