645407993 has 2 divisors, whose sum is σ = 645407994. Its totient is φ = 645407992.

The previous prime is 645407981. The next prime is 645408041. The reversal of 645407993 is 399704546.

It is a happy number.

645407993 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 427786489 + 217621504 = 20683^2 + 14752^2 .

It is a cyclic number.

It is not a de Polignac number, because 645407993 - 2⁶ = 645407929 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (645407923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322703996 + 322703997.

It is an arithmetic number, because the mean of its divisors is an integer number (322703997).

Almost surely, 2^645407993 is an apocalyptic number.

It is an amenable number.

645407993 is a deficient number, since it is larger than the sum of its proper divisors (1).

645407993 is an equidigital number, since it uses as much as digits as its factorization.

645407993 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 816480, while the sum is 47.

The square root of 645407993 is about 25404.8812829346. The cubic root of 645407993 is about 864.1943975765.

The spelling of 645407993 in words is "six hundred forty-five million, four hundred seven thousand, nine hundred ninety-three".