21243020 has 48 divisors (see below), whose sum is σ = 46061568. Its totient is φ = 8226240.

The previous prime is 21243011. The next prime is 21243023. The reversal of 21243020 is 2034212.

It is a junction number, because it is equal to n+sod(n) for n = 21242986 and 21243004.

It is not an unprimeable number, because it can be changed into a prime (21243023) 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, 111125 + ... + 111315.

It is an arithmetic number, because the mean of its divisors is an integer number (959616).

Almost surely, 2^21243020 is an apocalyptic number.

21243020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21243020 is an abundant number, since it is smaller than the sum of its proper divisors (24818548).

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

21243020 is a wasteful number, since it uses less digits than its factorization.

21243020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350 (or 348 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 21243020 is about 4609.0150791682. The cubic root of 21243020 is about 276.9525826032.

Adding to 21243020 its reverse (2034212), we get a palindrome (23277232).

The spelling of 21243020 in words is "twenty-one million, two hundred forty-three thousand, twenty".