21211201306566 has 12 divisors (see below), whose sum is σ = 45957602830932. Its totient is φ = 7070400435516.

The previous prime is 21211201306543. The next prime is 21211201306579. The reversal of 21211201306566 is 66560310211212.

21211201306566 is a `hidden beast` number, since 21 + 21 + 1 + 20 + 1 + 30 + 6 + 566 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 21211201306566.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 589200036276 + ... + 589200036311.

It is an arithmetic number, because the mean of its divisors is an integer number (3829800235911).

Almost surely, 2^{21211201306566} is an apocalyptic number.

21211201306566 is an abundant number, since it is smaller than the sum of its proper divisors (24746401524366).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21211201306566 is a wasteful number, since it uses less digits than its factorization.

21211201306566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1178400072595 (or 1178400072592 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

Adding to 21211201306566 its reverse (66560310211212), we get a palindrome (87771511517778).

The spelling of 21211201306566 in words is "twenty-one trillion, two hundred eleven billion, two hundred one million, three hundred six thousand, five hundred sixty-six".