21001222220 has 72 divisors (see below), whose sum is σ = 48721092000. Its totient is φ = 7598257920.

The previous prime is 21001222219. The next prime is 21001222223. The reversal of 21001222220 is 2222210012.

It is a junction number, because it is equal to n+sod(n) for n = 21001222195 and 21001222204.

It is not an unprimeable number, because it can be changed into a prime (21001222223) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 459776 + ... + 503384.

Almost surely, 2^21001222220 is an apocalyptic number.

21001222220 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 21001222220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24360546000).

21001222220 is an abundant number, since it is smaller than the sum of its proper divisors (27719869780).

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

21001222220 is a wasteful number, since it uses less digits than its factorization.

21001222220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43839 (or 43826 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

Adding to 21001222220 its reverse (2222210012), we get a palindrome (23223432232).

It can be divided in two parts, 210012 and 22220, that added together give a palindrome (232232).

The spelling of 21001222220 in words is "twenty-one billion, one million, two hundred twenty-two thousand, two hundred twenty".