21001453220 has 96 divisors (see below), whose sum is σ = 49391838720. Its totient is φ = 7436482560.

The previous prime is 21001453201. The next prime is 21001453229. The reversal of 21001453220 is 2235410012.

It is a super-2 number, since 2×21001453220² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21001453192 and 21001453201.

It is not an unprimeable number, because it can be changed into a prime (21001453229) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1260464 + ... + 1277016.

It is an arithmetic number, because the mean of its divisors is an integer number (514498320).

Almost surely, 2^21001453220 is an apocalyptic number.

21001453220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21001453220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24695919360).

21001453220 is an abundant number, since it is smaller than the sum of its proper divisors (28390385500).

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

21001453220 is a wasteful number, since it uses less digits than its factorization.

21001453220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16725 (or 16723 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

Adding to 21001453220 its reverse (2235410012), we get a palindrome (23236863232).

The spelling of 21001453220 in words is "twenty-one billion, one million, four hundred fifty-three thousand, two hundred twenty".