21243220020 has 72 divisors (see below), whose sum is σ = 70295752800. Its totient is φ = 5149871040.

The previous prime is 21243220007. The next prime is 21243220021. The reversal of 21243220020 is 2002234212.

21243220020 is a `hidden beast` number, since 2 + 12 + 432 + 200 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21243219975 and 21243220002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243220021) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5362470 + ... + 5366429.

It is an arithmetic number, because the mean of its divisors is an integer number (976329900).

Almost surely, 2^21243220020 is an apocalyptic number.

21243220020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21243220020 is an abundant number, since it is smaller than the sum of its proper divisors (49052532780).

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

21243220020 is a wasteful number, since it uses less digits than its factorization.

21243220020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10728925 (or 10728920 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

Adding to 21243220020 its reverse (2002234212), we get a palindrome (23245454232).

The spelling of 21243220020 in words is "twenty-one billion, two hundred forty-three million, two hundred twenty thousand, twenty".