21663411203821 has 2 divisors, whose sum is σ = 21663411203822. Its totient is φ = 21663411203820.

The previous prime is 21663411203803. The next prime is 21663411203849. The reversal of 21663411203821 is 12830211436612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17746420022500 + 3916991181321 = 4212650^2 + 1979139^2 .

It is a cyclic number.

It is not a de Polignac number, because 21663411203821 - 2²³ = 21663402815213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21663411203801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10831705601910 + 10831705601911.

It is an arithmetic number, because the mean of its divisors is an integer number (10831705601911).

Almost surely, 2^{21663411203821} is an apocalyptic number.

It is an amenable number.

21663411203821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21663411203821 is an equidigital number, since it uses as much as digits as its factorization.

21663411203821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 82944, while the sum is 40.

The spelling of 21663411203821 in words is "twenty-one trillion, six hundred sixty-three billion, four hundred eleven million, two hundred three thousand, eight hundred twenty-one".