644189263 has 2 divisors, whose sum is σ = 644189264. Its totient is φ = 644189262.

The previous prime is 644189251. The next prime is 644189309. The reversal of 644189263 is 362981446.

It is a happy number.

644189263 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 is a cyclic number.

It is not a de Polignac number, because 644189263 - 2²¹ = 642092111 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644189233) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322094631 + 322094632.

It is an arithmetic number, because the mean of its divisors is an integer number (322094632).

Almost surely, 2^644189263 is an apocalyptic number.

644189263 is a deficient number, since it is larger than the sum of its proper divisors (1).

644189263 is an equidigital number, since it uses as much as digits as its factorization.

644189263 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 248832, while the sum is 43.

The square root of 644189263 is about 25380.8838104586. The cubic root of 644189263 is about 863.6500993544.

The spelling of 644189263 in words is "six hundred forty-four million, one hundred eighty-nine thousand, two hundred sixty-three".