21121111220 has 96 divisors (see below), whose sum is σ = 50180860800. Its totient is φ = 7396928000.

The previous prime is 21121111153. The next prime is 21121111279. The reversal of 21121111220 is 2211112112.

It is a super-2 number, since 2×21121111220² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21121111195 and 21121111204.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2669270 + ... + 2677170.

It is an arithmetic number, because the mean of its divisors is an integer number (522717300).

Almost surely, 2^21121111220 is an apocalyptic number.

21121111220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21121111220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25090430400).

21121111220 is an abundant number, since it is smaller than the sum of its proper divisors (29059749580).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21121111220 is a wasteful number, since it uses less digits than its factorization.

21121111220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8369 (or 8367 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 14.

Adding to 21121111220 its reverse (2211112112), we get a palindrome (23332223332).

The spelling of 21121111220 in words is "twenty-one billion, one hundred twenty-one million, one hundred eleven thousand, two hundred twenty".