645738671 has 2 divisors, whose sum is σ = 645738672. Its totient is φ = 645738670.

The previous prime is 645738637. The next prime is 645738673. The reversal of 645738671 is 176837546.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645738671 is a prime.

Together with 645738673, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645738673) 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, 322869335 + 322869336.

It is an arithmetic number, because the mean of its divisors is an integer number (322869336).

Almost surely, 2^645738671 is an apocalyptic number.

645738671 is a deficient number, since it is larger than the sum of its proper divisors (1).

645738671 is an equidigital number, since it uses as much as digits as its factorization.

645738671 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 846720, while the sum is 47.

The square root of 645738671 is about 25411.3886082599. The cubic root of 645738671 is about 864.3419638120.

The spelling of 645738671 in words is "six hundred forty-five million, seven hundred thirty-eight thousand, six hundred seventy-one".