21666364536523 has 24 divisors (see below), whose sum is σ = 25377155204400. Its totient is φ = 18443424726720.

The previous prime is 21666364536511. The next prime is 21666364536541. The reversal of 21666364536523 is 32563546366612.

It is not a de Polignac number, because 21666364536523 - 2¹³ = 21666364528331 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21666364530523) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 43639465 + ... + 44133157.

It is an arithmetic number, because the mean of its divisors is an integer number (1057381466850).

Almost surely, 2^{21666364536523} is an apocalyptic number.

21666364536523 is a deficient number, since it is larger than the sum of its proper divisors (3710790667877).

21666364536523 is a wasteful number, since it uses less digits than its factorization.

21666364536523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 499867 (or 499860 counting only the distinct ones).

The product of its digits is 83980800, while the sum is 58.

The spelling of 21666364536523 in words is "twenty-one trillion, six hundred sixty-six billion, three hundred sixty-four million, five hundred thirty-six thousand, five hundred twenty-three".