21663205122553 has 2 divisors, whose sum is σ = 21663205122554. Its totient is φ = 21663205122552.

The previous prime is 21663205122439. The next prime is 21663205122563. The reversal of 21663205122553 is 35522150236612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21574092723264 + 89112399289 = 4644792^2 + 298517^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21663205122553 is a prime.

It is not a weakly prime, because it can be changed into another prime (21663205122563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10831602561276 + 10831602561277.

It is an arithmetic number, because the mean of its divisors is an integer number (10831602561277).

Almost surely, 2^{21663205122553} is an apocalyptic number.

It is an amenable number.

21663205122553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21663205122553 is an equidigital number, since it uses as much as digits as its factorization.

21663205122553 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648000, while the sum is 43.

The spelling of 21663205122553 in words is "twenty-one trillion, six hundred sixty-three billion, two hundred five million, one hundred twenty-two thousand, five hundred fifty-three".