251005421 has 2 divisors, whose sum is σ = 251005422. Its totient is φ = 251005420.

The previous prime is 251005399. The next prime is 251005441. The reversal of 251005421 is 124500152.

It is an a-pointer prime, because the next prime (251005441) can be obtained adding 251005421 to its sum of digits (20).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 159037321 + 91968100 = 12611^2 + 9590^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-251005421 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 251005393 and 251005402.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251005441) 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, 125502710 + 125502711.

It is an arithmetic number, because the mean of its divisors is an integer number (125502711).

Almost surely, 2^251005421 is an apocalyptic number.

It is an amenable number.

251005421 is a deficient number, since it is larger than the sum of its proper divisors (1).

251005421 is an equidigital number, since it uses as much as digits as its factorization.

251005421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 251005421 is about 15843.1506020741. The cubic root of 251005421 is about 630.8038960864.

Adding to 251005421 its reverse (124500152), we get a palindrome (375505573).

The spelling of 251005421 in words is "two hundred fifty-one million, five thousand, four hundred twenty-one".