644656403 has 2 divisors, whose sum is σ = 644656404. Its totient is φ = 644656402.

The previous prime is 644656391. The next prime is 644656409. The reversal of 644656403 is 304656446.

It is a happy number.

644656403 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644656403 - 2¹⁰ = 644655379 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (644656409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322328201 + 322328202.

It is an arithmetic number, because the mean of its divisors is an integer number (322328202).

Almost surely, 2^644656403 is an apocalyptic number.

644656403 is a deficient number, since it is larger than the sum of its proper divisors (1).

644656403 is an equidigital number, since it uses as much as digits as its factorization.

644656403 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 207360, while the sum is 38.

The square root of 644656403 is about 25390.0847379445. The cubic root of 644656403 is about 863.8588102872.

The spelling of 644656403 in words is "six hundred forty-four million, six hundred fifty-six thousand, four hundred three".