2166566665121 has 4 divisors (see below), whose sum is σ = 2241275860500. Its totient is φ = 2091857469744.

The previous prime is 2166566665117. The next prime is 2166566665127. The reversal of 2166566665121 is 1215666656612.

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 591953278225 + 1574613386896 = 769385^2 + 1254836^2 .

It is a cyclic number.

It is not a de Polignac number, because 2166566665121 - 2² = 2166566665117 is a prime.

It is a super-2 number, since 2×2166566665121² (a number of 25 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2166566665127) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37354597646 + ... + 37354597703.

It is an arithmetic number, because the mean of its divisors is an integer number (560318965125).

Almost surely, 2^{2166566665121} is an apocalyptic number.

It is an amenable number.

2166566665121 is a deficient number, since it is larger than the sum of its proper divisors (74709195379).

2166566665121 is an equidigital number, since it uses as much as digits as its factorization.

2166566665121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74709195378.

The product of its digits is 4665600, while the sum is 53.

The spelling of 2166566665121 in words is "two trillion, one hundred sixty-six billion, five hundred sixty-six million, six hundred sixty-five thousand, one hundred twenty-one".