251994221 has 2 divisors, whose sum is σ = 251994222. Its totient is φ = 251994220.

The previous prime is 251994217. The next prime is 251994227. The reversal of 251994221 is 122499152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 225420196 + 26574025 = 15014^2 + 5155^2 .

It is a cyclic number.

It is not a de Polignac number, because 251994221 - 2² = 251994217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251994227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125997110 + 125997111.

It is an arithmetic number, because the mean of its divisors is an integer number (125997111).

Almost surely, 2^251994221 is an apocalyptic number.

It is an amenable number.

251994221 is a deficient number, since it is larger than the sum of its proper divisors (1).

251994221 is an equidigital number, since it uses as much as digits as its factorization.

251994221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 35.

The square root of 251994221 is about 15874.3258439532. The cubic root of 251994221 is about 631.6311313898.

The spelling of 251994221 in words is "two hundred fifty-one million, nine hundred ninety-four thousand, two hundred twenty-one".