251266661 has 2 divisors, whose sum is σ = 251266662. Its totient is φ = 251266660.

The previous prime is 251266649. The next prime is 251266679. The reversal of 251266661 is 166662152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 202350625 + 48916036 = 14225^2 + 6994^2 .

It is a cyclic number.

It is not a de Polignac number, because 251266661 - 2¹⁸ = 251004517 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251266061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125633330 + 125633331.

It is an arithmetic number, because the mean of its divisors is an integer number (125633331).

Almost surely, 2^251266661 is an apocalyptic number.

It is an amenable number.

251266661 is a deficient number, since it is larger than the sum of its proper divisors (1).

251266661 is an equidigital number, since it uses as much as digits as its factorization.

251266661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25920, while the sum is 35.

The square root of 251266661 is about 15851.3930302671. The cubic root of 251266661 is about 631.0226617104.

The spelling of 251266661 in words is "two hundred fifty-one million, two hundred sixty-six thousand, six hundred sixty-one".