21212121111 has 8 divisors (see below), whose sum is σ = 28284163824. Its totient is φ = 14140746240.

The previous prime is 21212121109. The next prime is 21212121157. The reversal of 21212121111 is 11112121212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21212121111 - 2¹ = 21212121109 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212121181) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 87436 + ... + 223761.

It is an arithmetic number, because the mean of its divisors is an integer number (3535520478).

Almost surely, 2^21212121111 is an apocalyptic number.

21212121111 is a deficient number, since it is larger than the sum of its proper divisors (7072042713).

21212121111 is a wasteful number, since it uses less digits than its factorization.

21212121111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333921.

The product of its digits is 16, while the sum is 15.

Adding to 21212121111 its reverse (11112121212), we get a palindrome (32324242323).

It can be divided in two parts, 2121212 and 1111, that multiplied together give a palindrome (2356666532).

The spelling of 21212121111 in words is "twenty-one billion, two hundred twelve million, one hundred twenty-one thousand, one hundred eleven".