2221666661 has 2 divisors, whose sum is σ = 2221666662. Its totient is φ = 2221666660.

The previous prime is 2221666627. The next prime is 2221666663. The reversal of 2221666661 is 1666661222.

2221666661 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., 2123458561 + 98208100 = 46081^2 + 9910^2 .

It is a cyclic number.

It is not a de Polignac number, because 2221666661 - 2¹⁸ = 2221404517 is a prime.

Together with 2221666663, 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 (2221666663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1110833330 + 1110833331.

It is an arithmetic number, because the mean of its divisors is an integer number (1110833331).

Almost surely, 2^2221666661 is an apocalyptic number.

It is an amenable number.

2221666661 is a deficient number, since it is larger than the sum of its proper divisors (1).

2221666661 is an equidigital number, since it uses as much as digits as its factorization.

2221666661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 38.

The square root of 2221666661 is about 47134.5590941509. The cubic root of 2221666661 is about 1304.8471238934.

The spelling of 2221666661 in words is "two billion, two hundred twenty-one million, six hundred sixty-six thousand, six hundred sixty-one".