21011111220 has 48 divisors (see below), whose sum is σ = 64179396288. Its totient is φ = 5093602560.

The previous prime is 21011111203. The next prime is 21011111237. The reversal of 21011111220 is 2211111012.

It is an interprime number because it is at equal distance from previous prime (21011111203) and next prime (21011111237).

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21011111196 and 21011111205.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15916849 + ... + 15918168.

It is an arithmetic number, because the mean of its divisors is an integer number (1337070756).

Almost surely, 2^21011111220 is an apocalyptic number.

21011111220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21011111220 is an abundant number, since it is smaller than the sum of its proper divisors (43168285068).

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

21011111220 is a wasteful number, since it uses less digits than its factorization.

21011111220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31835040 (or 31835038 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 12.

Adding to 21011111220 its reverse (2211111012), we get a palindrome (23222222232).

It can be divided in two parts, 21011 and 111220, that added together give a palindrome (132231).

The spelling of 21011111220 in words is "twenty-one billion, eleven million, one hundred eleven thousand, two hundred twenty".