644352251 has 2 divisors, whose sum is σ = 644352252. Its totient is φ = 644352250.

The previous prime is 644352223. The next prime is 644352259. The reversal of 644352251 is 152253446.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644352251 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644352259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322176125 + 322176126.

It is an arithmetic number, because the mean of its divisors is an integer number (322176126).

Almost surely, 2^644352251 is an apocalyptic number.

644352251 is a deficient number, since it is larger than the sum of its proper divisors (1).

644352251 is an equidigital number, since it uses as much as digits as its factorization.

644352251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 28800, while the sum is 32.

The square root of 644352251 is about 25384.0944490837. The cubic root of 644352251 is about 863.7229313312.

The spelling of 644352251 in words is "six hundred forty-four million, three hundred fifty-two thousand, two hundred fifty-one".