266555566021 has 4 divisors (see below), whose sum is σ = 268253372332. Its totient is φ = 264857759712.

The previous prime is 266555566007. The next prime is 266555566027. The reversal of 266555566021 is 120665555662.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 67384372225 + 199171193796 = 259585^2 + 446286^2 .

It is a cyclic number.

It is not a de Polignac number, because 266555566021 - 2²¹ = 266553468869 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (266555566027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 848902920 + ... + 848903233.

It is an arithmetic number, because the mean of its divisors is an integer number (67063343083).

Almost surely, 2^266555566021 is an apocalyptic number.

It is an amenable number.

266555566021 is a deficient number, since it is larger than the sum of its proper divisors (1697806311).

266555566021 is a wasteful number, since it uses less digits than its factorization.

266555566021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1697806310.

The product of its (nonzero) digits is 3240000, while the sum is 49.

The spelling of 266555566021 in words is "two hundred sixty-six billion, five hundred fifty-five million, five hundred sixty-six thousand, twenty-one".