21213363206666 has 16 divisors (see below), whose sum is σ = 32816424182784. Its totient is φ = 10278439665984.

The previous prime is 21213363206561. The next prime is 21213363206689. The reversal of 21213363206666 is 66660236331212.

It is a self number, because there is not a number n which added to its sum of digits gives 21213363206666.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 971119055 + ... + 971140898.

It is an arithmetic number, because the mean of its divisors is an integer number (2051026511424).

Almost surely, 2^{21213363206666} is an apocalyptic number.

21213363206666 is a deficient number, since it is larger than the sum of its proper divisors (11603060976118).

21213363206666 is a wasteful number, since it uses less digits than its factorization.

21213363206666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1942260125.

The product of its (nonzero) digits is 1679616, while the sum is 47.

Adding to 21213363206666 its reverse (66660236331212), we get a palindrome (87873599537878).

The spelling of 21213363206666 in words is "twenty-one trillion, two hundred thirteen billion, three hundred sixty-three million, two hundred six thousand, six hundred sixty-six".