251216321 has 2 divisors, whose sum is σ = 251216322. Its totient is φ = 251216320.

The previous prime is 251216311. The next prime is 251216351. The reversal of 251216321 is 123612152.

251216321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 131423296 + 119793025 = 11464^2 + 10945^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-251216321 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (251216311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125608160 + 125608161.

It is an arithmetic number, because the mean of its divisors is an integer number (125608161).

Almost surely, 2^251216321 is an apocalyptic number.

It is an amenable number.

251216321 is a deficient number, since it is larger than the sum of its proper divisors (1).

251216321 is an equidigital number, since it uses as much as digits as its factorization.

251216321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 720, while the sum is 23.

The square root of 251216321 is about 15849.8050776658. The cubic root of 251216321 is about 630.9805181669.

Adding to 251216321 its reverse (123612152), we get a palindrome (374828473).

The spelling of 251216321 in words is "two hundred fifty-one million, two hundred sixteen thousand, three hundred twenty-one".