21843996661 has 2 divisors, whose sum is σ = 21843996662. Its totient is φ = 21843996660.

The previous prime is 21843996641. The next prime is 21843996731. The reversal of 21843996661 is 16669934812.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21695522436 + 148474225 = 147294^2 + 12185^2 .

It is a cyclic number.

It is not a de Polignac number, because 21843996661 - 2²⁵ = 21810442229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21843996631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10921998330 + 10921998331.

It is an arithmetic number, because the mean of its divisors is an integer number (10921998331).

Almost surely, 2^21843996661 is an apocalyptic number.

It is an amenable number.

21843996661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21843996661 is an equidigital number, since it uses as much as digits as its factorization.

21843996661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3359232, while the sum is 55.

The spelling of 21843996661 in words is "twenty-one billion, eight hundred forty-three million, nine hundred ninety-six thousand, six hundred sixty-one".