21121111213 has 4 divisors (see below), whose sum is σ = 21330231228. Its totient is φ = 20911991200.

The previous prime is 21121111153. The next prime is 21121111279. The reversal of 21121111213 is 31211112112.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19113892009 + 2007219204 = 138253^2 + 44802^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121111213 - 2²⁹ = 20584240301 is a prime.

It is a super-2 number, since 2×21121111213² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121141213) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 104559856 + ... + 104560057.

It is an arithmetic number, because the mean of its divisors is an integer number (5332557807).

Almost surely, 2^21121111213 is an apocalyptic number.

It is an amenable number.

21121111213 is a deficient number, since it is larger than the sum of its proper divisors (209120015).

21121111213 is a wasteful number, since it uses less digits than its factorization.

21121111213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 209120014.

The product of its digits is 24, while the sum is 16.

Adding to 21121111213 its reverse (31211112112), we get a palindrome (52332223325).

The spelling of 21121111213 in words is "twenty-one billion, one hundred twenty-one million, one hundred eleven thousand, two hundred thirteen".