21000122220 has 192 divisors, whose sum is σ = 74404786176. Its totient is φ = 4298469120.

The previous prime is 21000122201. The next prime is 21000122233. The reversal of 21000122220 is 2222100012.

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 = 21000122196 and 21000122205.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 275619 + ... + 343461.

It is an arithmetic number, because the mean of its divisors is an integer number (387524928).

Almost surely, 2^21000122220 is an apocalyptic number.

21000122220 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 21000122220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37202393088).

21000122220 is an abundant number, since it is smaller than the sum of its proper divisors (53404663956).

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

21000122220 is a wasteful number, since it uses less digits than its factorization.

21000122220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67940 (or 67938 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 12.

Adding to 21000122220 its reverse (2222100012), we get a palindrome (23222222232).

It can be divided in two parts, 210001 and 22220, that added together give a triangular number (232221 = T₆₈₁).

The spelling of 21000122220 in words is "twenty-one billion, one hundred twenty-two thousand, two hundred twenty".