2666816021 has 2 divisors, whose sum is σ = 2666816022. Its totient is φ = 2666816020.

The previous prime is 2666815997. The next prime is 2666816023. The reversal of 2666816021 is 1206186662.

2666816021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1965148900 + 701667121 = 44330^2 + 26489^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2666816021 is a prime.

It is a super-2 number, since 2×2666816021² = 14223815379724544882, which contains 22 as substring.

Together with 2666816023, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2666816023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1333408010 + 1333408011.

It is an arithmetic number, because the mean of its divisors is an integer number (1333408011).

Almost surely, 2^2666816021 is an apocalyptic number.

It is an amenable number.

2666816021 is a deficient number, since it is larger than the sum of its proper divisors (1).

2666816021 is an equidigital number, since it uses as much as digits as its factorization.

2666816021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 41472, while the sum is 38.

The square root of 2666816021 is about 51641.2240462985. The cubic root of 2666816021 is about 1386.7484373457.

The spelling of 2666816021 in words is "two billion, six hundred sixty-six million, eight hundred sixteen thousand, twenty-one".