666889261 has 2 divisors, whose sum is σ = 666889262. Its totient is φ = 666889260.

The previous prime is 666889247. The next prime is 666889273. The reversal of 666889261 is 162988666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 505980036 + 160909225 = 22494^2 + 12685^2 .

It is a cyclic number.

It is not a de Polignac number, because 666889261 - 2¹³ = 666881069 is a prime.

It is a super-2 number, since 2×666889261² = 889482572874252242, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 666889199 and 666889208.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666889211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333444630 + 333444631.

It is an arithmetic number, because the mean of its divisors is an integer number (333444631).

Almost surely, 2^666889261 is an apocalyptic number.

It is an amenable number.

666889261 is a deficient number, since it is larger than the sum of its proper divisors (1).

666889261 is an equidigital number, since it uses as much as digits as its factorization.

666889261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1492992, while the sum is 52.

The square root of 666889261 is about 25824.1991356944. The cubic root of 666889261 is about 873.6776809478.

The spelling of 666889261 in words is "six hundred sixty-six million, eight hundred eighty-nine thousand, two hundred sixty-one".