645861217 has 2 divisors, whose sum is σ = 645861218. Its totient is φ = 645861216.

The previous prime is 645861193. The next prime is 645861287. The reversal of 645861217 is 712168546.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 644956816 + 904401 = 25396^2 + 951^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645861217 is a prime.

It is equal to p_33589381 and since 645861217 and 33589381 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 645861217.

It is not a weakly prime, because it can be changed into another prime (645861287) 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, 322930608 + 322930609.

It is an arithmetic number, because the mean of its divisors is an integer number (322930609).

Almost surely, 2^645861217 is an apocalyptic number.

It is an amenable number.

645861217 is a deficient number, since it is larger than the sum of its proper divisors (1).

645861217 is an equidigital number, since it uses as much as digits as its factorization.

645861217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 80640, while the sum is 40.

The square root of 645861217 is about 25413.7997355767. The cubic root of 645861217 is about 864.3966376067.

The spelling of 645861217 in words is "six hundred forty-five million, eight hundred sixty-one thousand, two hundred seventeen".