645720671 has 2 divisors, whose sum is σ = 645720672. Its totient is φ = 645720670.

The previous prime is 645720629. The next prime is 645720701. The reversal of 645720671 is 176027546.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 645720671 - 2¹⁰ = 645719647 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645720601) 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, 322860335 + 322860336.

It is an arithmetic number, because the mean of its divisors is an integer number (322860336).

Almost surely, 2^645720671 is an apocalyptic number.

645720671 is a deficient number, since it is larger than the sum of its proper divisors (1).

645720671 is an equidigital number, since it uses as much as digits as its factorization.

645720671 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 70560, while the sum is 38.

The square root of 645720671 is about 25411.0344338832. The cubic root of 645720671 is about 864.3339325446. Note that the first 3 decimals are identical.

The spelling of 645720671 in words is "six hundred forty-five million, seven hundred twenty thousand, six hundred seventy-one".