21021220111 has 4 divisors (see below), whose sum is σ = 21746089800. Its totient is φ = 20296350424.

The previous prime is 21021220081. The next prime is 21021220117. The reversal of 21021220111 is 11102212012.

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 21021220111 - 2³¹ = 18873736463 is a prime.

It is a super-2 number, since 2×21021220111² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021220091 and 21021220100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021220117) 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, 362434801 + ... + 362434858.

It is an arithmetic number, because the mean of its divisors is an integer number (5436522450).

Almost surely, 2^21021220111 is an apocalyptic number.

21021220111 is a deficient number, since it is larger than the sum of its proper divisors (724869689).

21021220111 is an equidigital number, since it uses as much as digits as its factorization.

21021220111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724869688.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21021220111 its reverse (11102212012), we get a palindrome (32123432123).

The spelling of 21021220111 in words is "twenty-one billion, twenty-one million, two hundred twenty thousand, one hundred eleven".