21003121220 has 24 divisors (see below), whose sum is σ = 44122112664. Its totient is φ = 8398285056.

The previous prime is 21003121213. The next prime is 21003121241. The reversal of 21003121220 is 2212130012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 4766245444 + 16236875776 = 69038^2 + 127424^2 .

It is a super-2 number, since 2×21003121220² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21003121195 and 21003121204.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 126647 + ... + 240926.

It is an arithmetic number, because the mean of its divisors is an integer number (1838421361).

Almost surely, 2^21003121220 is an apocalyptic number.

21003121220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21003121220 is an abundant number, since it is smaller than the sum of its proper divisors (23118991444).

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

21003121220 is a wasteful number, since it uses less digits than its factorization.

21003121220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 370439 (or 370437 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 14.

Adding to 21003121220 its reverse (2212130012), we get a palindrome (23215251232).

The spelling of 21003121220 in words is "twenty-one billion, three million, one hundred twenty-one thousand, two hundred twenty".