251665901 has 2 divisors, whose sum is σ = 251665902. Its totient is φ = 251665900.

The previous prime is 251665891. The next prime is 251665919. The reversal of 251665901 is 109566152.

251665901 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., 182277001 + 69388900 = 13501^2 + 8330^2 .

It is a cyclic number.

It is not a de Polignac number, because 251665901 - 2⁶ = 251665837 is a prime.

It is a super-2 number, since 2×251665901² = 126671451452283602, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251665951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125832950 + 125832951.

It is an arithmetic number, because the mean of its divisors is an integer number (125832951).

Almost surely, 2^251665901 is an apocalyptic number.

It is an amenable number.

251665901 is a deficient number, since it is larger than the sum of its proper divisors (1).

251665901 is an equidigital number, since it uses as much as digits as its factorization.

251665901 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16200, while the sum is 35.

The square root of 251665901 is about 15863.9812468371. The cubic root of 251665901 is about 631.3566975021.

The spelling of 251665901 in words is "two hundred fifty-one million, six hundred sixty-five thousand, nine hundred one".