251961421 has 2 divisors, whose sum is σ = 251961422. Its totient is φ = 251961420.

The previous prime is 251961371. The next prime is 251961433. The reversal of 251961421 is 124169152.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 239816196 + 12145225 = 15486^2 + 3485^2 .

It is a cyclic number.

It is not a de Polignac number, because 251961421 - 2⁹ = 251960909 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251961491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125980710 + 125980711.

It is an arithmetic number, because the mean of its divisors is an integer number (125980711).

Almost surely, 2^251961421 is an apocalyptic number.

It is an amenable number.

251961421 is a deficient number, since it is larger than the sum of its proper divisors (1).

251961421 is an equidigital number, since it uses as much as digits as its factorization.

251961421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 31.

The square root of 251961421 is about 15873.2926955941. The cubic root of 251961421 is about 631.6037254703.

The spelling of 251961421 in words is "two hundred fifty-one million, nine hundred sixty-one thousand, four hundred twenty-one".