21202121220 has 48 divisors (see below), whose sum is σ = 67846789248. Its totient is φ = 4846199040.

The previous prime is 21202121207. The next prime is 21202121221. The reversal of 21202121220 is 2212120212.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21202121220.

It is not an unprimeable number, because it can be changed into a prime (21202121221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25240201 + ... + 25241040.

It is an arithmetic number, because the mean of its divisors is an integer number (1413474776).

Almost surely, 2^21202121220 is an apocalyptic number.

21202121220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21202121220 is an abundant number, since it is smaller than the sum of its proper divisors (46644668028).

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

21202121220 is a wasteful number, since it uses less digits than its factorization.

21202121220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50481260 (or 50481258 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

Adding to 21202121220 its reverse (2212120212), we get a palindrome (23414241432).

The spelling of 21202121220 in words is "twenty-one billion, two hundred two million, one hundred twenty-one thousand, two hundred twenty".