21001220111 has 4 divisors (see below), whose sum is σ = 21058444512. Its totient is φ = 20943995712.

The previous prime is 21001220099. The next prime is 21001220153. The reversal of 21001220111 is 11102210012.

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 21001220111 - 2¹⁰ = 21001219087 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001220092 and 21001220101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001220171) 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, 28611650 + ... + 28612383.

It is an arithmetic number, because the mean of its divisors is an integer number (5264611128).

Almost surely, 2^21001220111 is an apocalyptic number.

21001220111 is a deficient number, since it is larger than the sum of its proper divisors (57224401).

21001220111 is an equidigital number, since it uses as much as digits as its factorization.

21001220111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57224400.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21001220111 its reverse (11102210012), we get a palindrome (32103430123).

The spelling of 21001220111 in words is "twenty-one billion, one million, two hundred twenty thousand, one hundred eleven".