644209243 has 2 divisors, whose sum is σ = 644209244. Its totient is φ = 644209242.

The previous prime is 644209217. The next prime is 644209283. The reversal of 644209243 is 342902446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644209243 - 2⁵ = 644209211 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644209199 and 644209208.

It is not a weakly prime, because it can be changed into another prime (644209283) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322104621 + 322104622.

It is an arithmetic number, because the mean of its divisors is an integer number (322104622).

Almost surely, 2^644209243 is an apocalyptic number.

644209243 is a deficient number, since it is larger than the sum of its proper divisors (1).

644209243 is an equidigital number, since it uses as much as digits as its factorization.

644209243 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 41472, while the sum is 34.

The square root of 644209243 is about 25381.2774107215. The cubic root of 644209243 is about 863.6590281748.

The spelling of 644209243 in words is "six hundred forty-four million, two hundred nine thousand, two hundred forty-three".