644646427 has 2 divisors, whose sum is σ = 644646428. Its totient is φ = 644646426.

The previous prime is 644646413. The next prime is 644646433. The reversal of 644646427 is 724646446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644646427 - 2¹¹ = 644644379 is a prime.

It is not a weakly prime, because it can be changed into another prime (644646487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322323213 + 322323214.

It is an arithmetic number, because the mean of its divisors is an integer number (322323214).

Almost surely, 2^644646427 is an apocalyptic number.

644646427 is a deficient number, since it is larger than the sum of its proper divisors (1).

644646427 is an equidigital number, since it uses as much as digits as its factorization.

644646427 is an evil number, because the sum of its binary digits is even.

The product of its digits is 774144, while the sum is 43.

The square root of 644646427 is about 25389.8882825427. Note that the first 3 decimals coincide. The cubic root of 644646427 is about 863.8543542184.

The spelling of 644646427 in words is "six hundred forty-four million, six hundred forty-six thousand, four hundred twenty-seven".