645205663 has 2 divisors, whose sum is σ = 645205664. Its totient is φ = 645205662.

The previous prime is 645205661. The next prime is 645205721. The reversal of 645205663 is 366502546.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 645205663 - 2¹ = 645205661 is a prime.

Together with 645205661, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645205661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322602831 + 322602832.

It is an arithmetic number, because the mean of its divisors is an integer number (322602832).

Almost surely, 2^645205663 is an apocalyptic number.

645205663 is a deficient number, since it is larger than the sum of its proper divisors (1).

645205663 is an equidigital number, since it uses as much as digits as its factorization.

645205663 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 37.

The square root of 645205663 is about 25400.8988620482. The cubic root of 645205663 is about 864.1040822364.

The spelling of 645205663 in words is "six hundred forty-five million, two hundred five thousand, six hundred sixty-three".