251121317 has 2 divisors, whose sum is σ = 251121318. Its totient is φ = 251121316.

The previous prime is 251121307. The next prime is 251121319. The reversal of 251121317 is 713121152.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 249924481 + 1196836 = 15809^2 + 1094^2 .

It is a cyclic number.

It is not a de Polignac number, because 251121317 - 2⁴ = 251121301 is a prime.

Together with 251121319, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 251121292 and 251121301.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251121319) 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, 125560658 + 125560659.

It is an arithmetic number, because the mean of its divisors is an integer number (125560659).

Almost surely, 2^251121317 is an apocalyptic number.

It is an amenable number.

251121317 is a deficient number, since it is larger than the sum of its proper divisors (1).

251121317 is an equidigital number, since it uses as much as digits as its factorization.

251121317 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 420, while the sum is 23.

The square root of 251121317 is about 15846.8077857971. The cubic root of 251121317 is about 630.9009675613.

Adding to 251121317 its reverse (713121152), we get a palindrome (964242469).

The spelling of 251121317 in words is "two hundred fifty-one million, one hundred twenty-one thousand, three hundred seventeen".