665425181 has 2 divisors, whose sum is σ = 665425182. Its totient is φ = 665425180.

The previous prime is 665425157. The next prime is 665425253. The reversal of 665425181 is 181524566.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 657101956 + 8323225 = 25634^2 + 2885^2 .

It is a cyclic number.

It is not a de Polignac number, because 665425181 - 2²⁶ = 598316317 is a prime.

It is a super-2 number, since 2×665425181² = 885581343017765522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665425151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332712590 + 332712591.

It is an arithmetic number, because the mean of its divisors is an integer number (332712591).

Almost surely, 2^665425181 is an apocalyptic number.

It is an amenable number.

665425181 is a deficient number, since it is larger than the sum of its proper divisors (1).

665425181 is an equidigital number, since it uses as much as digits as its factorization.

665425181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 57600, while the sum is 38.

The square root of 665425181 is about 25795.8365051417. The cubic root of 665425181 is about 873.0378589653.

The spelling of 665425181 in words is "six hundred sixty-five million, four hundred twenty-five thousand, one hundred eighty-one".