21663561260623 has 2 divisors, whose sum is σ = 21663561260624. Its totient is φ = 21663561260622.

The previous prime is 21663561260531. The next prime is 21663561260633. The reversal of 21663561260623 is 32606216536612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21663561260623 - 2⁹ = 21663561260111 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21663561260633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10831780630311 + 10831780630312.

It is an arithmetic number, because the mean of its divisors is an integer number (10831780630312).

Almost surely, 2^{21663561260623} is an apocalyptic number.

21663561260623 is a deficient number, since it is larger than the sum of its proper divisors (1).

21663561260623 is an equidigital number, since it uses as much as digits as its factorization.

21663561260623 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2799360, while the sum is 49.

The spelling of 21663561260623 in words is "twenty-one trillion, six hundred sixty-three billion, five hundred sixty-one million, two hundred sixty thousand, six hundred twenty-three".