266666581 has 2 divisors, whose sum is σ = 266666582. Its totient is φ = 266666580.

The previous prime is 266666549. The next prime is 266666657. The reversal of 266666581 is 185666662.

266666581 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., 262926225 + 3740356 = 16215^2 + 1934^2 .

It is a cyclic number.

It is not a de Polignac number, because 266666581 - 2⁵ = 266666549 is a prime.

It is a super-2 number, since 2×266666581² = 142222130844459122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (266666381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 133333290 + 133333291.

It is an arithmetic number, because the mean of its divisors is an integer number (133333291).

Almost surely, 2^266666581 is an apocalyptic number.

It is an amenable number.

266666581 is a deficient number, since it is larger than the sum of its proper divisors (1).

266666581 is an equidigital number, since it uses as much as digits as its factorization.

266666581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 622080, while the sum is 46.

The square root of 266666581 is about 16329.9289955590. The cubic root of 266666581 is about 643.6595208119.

The spelling of 266666581 in words is "two hundred sixty-six million, six hundred sixty-six thousand, five hundred eighty-one".