21031031220 has 48 divisors (see below), whose sum is σ = 61986200640. Its totient is φ = 5313102336.

The previous prime is 21031031149. The next prime is 21031031227. The reversal of 21031031220 is 2213013012.

It is a super-2 number, since 2×21031031220² (a number of 21 digits) contains 22 as substring.

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 21031031220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21031031227) 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, 9222997 + ... + 9225276.

It is an arithmetic number, because the mean of its divisors is an integer number (1291379180).

Almost surely, 2^21031031220 is an apocalyptic number.

21031031220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21031031220 is an abundant number, since it is smaller than the sum of its proper divisors (40955169420).

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

21031031220 is a wasteful number, since it uses less digits than its factorization.

21031031220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18448304 (or 18448302 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 15.

Adding to 21031031220 its reverse (2213013012), we get a palindrome (23244044232).

The spelling of 21031031220 in words is "twenty-one billion, thirty-one million, thirty-one thousand, two hundred twenty".