21661699809793 has 2 divisors, whose sum is σ = 21661699809794. Its totient is φ = 21661699809792.

The previous prime is 21661699809703. The next prime is 21661699809839. The reversal of 21661699809793 is 39790899616612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15632597700864 + 6029102108929 = 3953808^2 + 2455423^2 .

It is a cyclic number.

It is not a de Polignac number, because 21661699809793 - 2²⁹ = 21661162938881 is a prime.

It is not a weakly prime, because it can be changed into another prime (21661699809703) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830849904896 + 10830849904897.

It is an arithmetic number, because the mean of its divisors is an integer number (10830849904897).

Almost surely, 2^{21661699809793} is an apocalyptic number.

It is an amenable number.

21661699809793 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661699809793 is an equidigital number, since it uses as much as digits as its factorization.

21661699809793 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 476171136, while the sum is 76.

The spelling of 21661699809793 in words is "twenty-one trillion, six hundred sixty-one billion, six hundred ninety-nine million, eight hundred nine thousand, seven hundred ninety-three".