644630279 has 2 divisors, whose sum is σ = 644630280. Its totient is φ = 644630278.

The previous prime is 644630267. The next prime is 644630297. The reversal of 644630279 is 972036446.

Together with next prime (644630297) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644630279 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644633279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322315139 + 322315140.

It is an arithmetic number, because the mean of its divisors is an integer number (322315140).

Almost surely, 2^644630279 is an apocalyptic number.

644630279 is a deficient number, since it is larger than the sum of its proper divisors (1).

644630279 is an equidigital number, since it uses as much as digits as its factorization.

644630279 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 217728, while the sum is 41.

The square root of 644630279 is about 25389.5702799398. The cubic root of 644630279 is about 863.8471411498.

The spelling of 644630279 in words is "six hundred forty-four million, six hundred thirty thousand, two hundred seventy-nine".