21606565997503 has 2 divisors, whose sum is σ = 21606565997504. Its totient is φ = 21606565997502.

The previous prime is 21606565997479. The next prime is 21606565997509. The reversal of 21606565997503 is 30579956560612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21606565997503 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21606565997509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10803282998751 + 10803282998752.

It is an arithmetic number, because the mean of its divisors is an integer number (10803282998752).

Almost surely, 2^{21606565997503} is an apocalyptic number.

21606565997503 is a deficient number, since it is larger than the sum of its proper divisors (1).

21606565997503 is an equidigital number, since it uses as much as digits as its factorization.

21606565997503 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 91854000, while the sum is 64.

The spelling of 21606565997503 in words is "twenty-one trillion, six hundred six billion, five hundred sixty-five million, nine hundred ninety-seven thousand, five hundred three".