645805903 has 2 divisors, whose sum is σ = 645805904. Its totient is φ = 645805902.

The previous prime is 645805873. The next prime is 645805907. The reversal of 645805903 is 309508546.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 645805903 - 2¹⁷ = 645674831 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645805907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322902951 + 322902952.

It is an arithmetic number, because the mean of its divisors is an integer number (322902952).

Almost surely, 2^645805903 is an apocalyptic number.

645805903 is a deficient number, since it is larger than the sum of its proper divisors (1).

645805903 is an equidigital number, since it uses as much as digits as its factorization.

645805903 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 129600, while the sum is 40.

The square root of 645805903 is about 25412.7114452590. The cubic root of 645805903 is about 864.3719601686.

The spelling of 645805903 in words is "six hundred forty-five million, eight hundred five thousand, nine hundred three".