21243021 has 8 divisors (see below), whose sum is σ = 28682880. Its totient is φ = 13982592.

The previous prime is 21243011. The next prime is 21243023. The reversal of 21243021 is 12034212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21243021 - 2⁶ = 21242957 is a prime.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 44580 + ... + 45053.

It is an arithmetic number, because the mean of its divisors is an integer number (3585360).

Almost surely, 2^21243021 is an apocalyptic number.

It is an amenable number.

21243021 is a deficient number, since it is larger than the sum of its proper divisors (7439859).

21243021 is an equidigital number, since it uses as much as digits as its factorization.

21243021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89715.

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

The square root of 21243021 is about 4609.0151876513. The cubic root of 21243021 is about 276.9525869490.

Adding to 21243021 its reverse (12034212), we get a palindrome (33277233).

The spelling of 21243021 in words is "twenty-one million, two hundred forty-three thousand, twenty-one".