645738673 has 2 divisors, whose sum is σ = 645738674.
Its totient is φ = 645738672.
The previous prime is 645738671. The next prime is 645738707. The reversal of 645738673 is 376837546.
It is a happy number.
645738673 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., 345513744 + 300224929 = 18588^2 + 17327^2
It is a cyclic number.
It is not a de Polignac number, because 645738673 - 21 = 645738671 is a prime.
Together with 645738671, it forms a pair of twin primes.
It is not a weakly prime, because it can be changed into another prime (645738671) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322869336 + 322869337.
It is an arithmetic number, because the mean of its divisors is an integer number (322869337).
Almost surely, 2645738673 is an apocalyptic number.
It is an amenable number.
645738673 is a deficient number, since it is larger than the sum of its proper divisors (1).
645738673 is an equidigital number, since it uses as much as digits as its factorization.
645738673 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 2540160, while the sum is 49.
The square root of 645738673 is about 25411.3886476123.
The cubic root of 645738673 is about 864.3419647044.
The spelling of 645738673 in words is "six hundred forty-five million, seven hundred thirty-eight thousand, six hundred seventy-three".