21205120220 has 48 divisors (see below), whose sum is σ = 44859678528. Its totient is φ = 8419507200.

The previous prime is 21205120217. The next prime is 21205120229. The reversal of 21205120220 is 2202150212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205120229) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3768329 + ... + 3773951.

It is an arithmetic number, because the mean of its divisors is an integer number (934576636).

Almost surely, 2^21205120220 is an apocalyptic number.

21205120220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21205120220 is an abundant number, since it is smaller than the sum of its proper divisors (23654558308).

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

21205120220 is a wasteful number, since it uses less digits than its factorization.

21205120220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6990 (or 6988 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 17.

Adding to 21205120220 its reverse (2202150212), we get a palindrome (23407270432).

The spelling of 21205120220 in words is "twenty-one billion, two hundred five million, one hundred twenty thousand, two hundred twenty".