21122221111 has 4 divisors (see below), whose sum is σ = 21209865424. Its totient is φ = 21034576800.

The previous prime is 21122221037. The next prime is 21122221121. The reversal of 21122221111 is 11112222112.

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 21122221111 - 2²³ = 21113832503 is a prime.

It is a super-2 number, since 2×21122221111² (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 (21122221121) 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, 43821795 + ... + 43822276.

It is an arithmetic number, because the mean of its divisors is an integer number (5302466356).

Almost surely, 2^21122221111 is an apocalyptic number.

21122221111 is a deficient number, since it is larger than the sum of its proper divisors (87644313).

21122221111 is an equidigital number, since it uses as much as digits as its factorization.

21122221111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87644312.

The product of its digits is 32, while the sum is 16.

Adding to 21122221111 its reverse (11112222112), we get a palindrome (32234443223).

It can be divided in two parts, 2112222111 and 1, that added together give a palindrome (2112222112).

The spelling of 21122221111 in words is "twenty-one billion, one hundred twenty-two million, two hundred twenty-one thousand, one hundred eleven".