21660973549 has 2 divisors, whose sum is σ = 21660973550. Its totient is φ = 21660973548.

The previous prime is 21660973513. The next prime is 21660973561. The reversal of 21660973549 is 94537906612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18095092324 + 3565881225 = 134518^2 + 59715^2 .

It is a cyclic number.

It is not a de Polignac number, because 21660973549 - 2⁷ = 21660973421 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21660973496 and 21660973505.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21660973349) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830486774 + 10830486775.

It is an arithmetic number, because the mean of its divisors is an integer number (10830486775).

Almost surely, 2^21660973549 is an apocalyptic number.

It is an amenable number.

21660973549 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660973549 is an equidigital number, since it uses as much as digits as its factorization.

21660973549 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2449440, while the sum is 52.

The spelling of 21660973549 in words is "twenty-one billion, six hundred sixty million, nine hundred seventy-three thousand, five hundred forty-nine".