21660353656091 has 2 divisors, whose sum is σ = 21660353656092. Its totient is φ = 21660353656090.

The previous prime is 21660353656057. The next prime is 21660353656211. The reversal of 21660353656091 is 19065635306612.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21660353656091 is a prime.

It is not a weakly prime, because it can be changed into another prime (21660353656021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830176828045 + 10830176828046.

It is an arithmetic number, because the mean of its divisors is an integer number (10830176828046).

Almost surely, 2^{21660353656091} is an apocalyptic number.

21660353656091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660353656091 is an equidigital number, since it uses as much as digits as its factorization.

21660353656091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5248800, while the sum is 53.

The spelling of 21660353656091 in words is "twenty-one trillion, six hundred sixty billion, three hundred fifty-three million, six hundred fifty-six thousand, ninety-one".