21001232220 has 24 divisors (see below), whose sum is σ = 58803450384. Its totient is φ = 5600328576.

The previous prime is 21001232179. The next prime is 21001232233. The reversal of 21001232220 is 2223210012.

It is a happy number.

It is a super-2 number, since 2×21001232220² (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 21001232220.

It is a congruent number.

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, 175010209 + ... + 175010328.

It is an arithmetic number, because the mean of its divisors is an integer number (2450143766).

Almost surely, 2^21001232220 is an apocalyptic number.

21001232220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001232220 is an abundant number, since it is smaller than the sum of its proper divisors (37802218164).

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

21001232220 is a wasteful number, since it uses less digits than its factorization.

21001232220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350020549 (or 350020547 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

Adding to 21001232220 its reverse (2223210012), we get a palindrome (23224442232).

The spelling of 21001232220 in words is "twenty-one billion, one million, two hundred thirty-two thousand, two hundred twenty".