21212111201 has 4 divisors (see below), whose sum is σ = 21212416452. Its totient is φ = 21211805952.

The previous prime is 21212111191. The next prime is 21212111209. The reversal of 21212111201 is 10211121212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 17512552225 + 3699558976 = 132335^2 + 60824^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212111201 - 2²² = 21207916897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21212111209) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7865 + ... + 206121.

It is an arithmetic number, because the mean of its divisors is an integer number (5303104113).

Almost surely, 2^21212111201 is an apocalyptic number.

It is an amenable number.

21212111201 is a deficient number, since it is larger than the sum of its proper divisors (305251).

21212111201 is a wasteful number, since it uses less digits than its factorization.

21212111201 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 305250.

The product of its (nonzero) digits is 16, while the sum is 14.

Adding to 21212111201 its reverse (10211121212), we get a palindrome (31423232413).

It can be divided in two parts, 212121 and 11201, that added together give a palindrome (223322).

The spelling of 21212111201 in words is "twenty-one billion, two hundred twelve million, one hundred eleven thousand, two hundred one".