251640317 has 2 divisors, whose sum is σ = 251640318. Its totient is φ = 251640316.

The previous prime is 251640287. The next prime is 251640349. The reversal of 251640317 is 713046152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 189640441 + 61999876 = 13771^2 + 7874^2 .

It is a cyclic number.

It is not a de Polignac number, because 251640317 - 2⁶ = 251640253 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 251640317.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251648317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125820158 + 125820159.

It is an arithmetic number, because the mean of its divisors is an integer number (125820159).

Almost surely, 2^251640317 is an apocalyptic number.

It is an amenable number.

251640317 is a deficient number, since it is larger than the sum of its proper divisors (1).

251640317 is an equidigital number, since it uses as much as digits as its factorization.

251640317 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5040, while the sum is 29.

The square root of 251640317 is about 15863.1748713806. The cubic root of 251640317 is about 631.3353025004.

Adding to 251640317 its reverse (713046152), we get a palindrome (964686469).

The spelling of 251640317 in words is "two hundred fifty-one million, six hundred forty thousand, three hundred seventeen".