21011212111 has 4 divisors (see below), whose sum is σ = 22117065400. Its totient is φ = 19905358824.

The previous prime is 21011212093. The next prime is 21011212121. The reversal of 21011212111 is 11121211012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21011212111 - 2¹¹ = 21011210063 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011212091 and 21011212100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011212121) 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, 552926616 + ... + 552926653.

It is an arithmetic number, because the mean of its divisors is an integer number (5529266350).

Almost surely, 2^21011212111 is an apocalyptic number.

21011212111 is a deficient number, since it is larger than the sum of its proper divisors (1105853289).

21011212111 is a wasteful number, since it uses less digits than its factorization.

21011212111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1105853288.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21011212111 its reverse (11121211012), we get a palindrome (32132423123).

The spelling of 21011212111 in words is "twenty-one billion, eleven million, two hundred twelve thousand, one hundred eleven".