21333521 has 8 divisors (see below), whose sum is σ = 24642144. Its totient is φ = 18253120.

The previous prime is 21333511. The next prime is 21333539. The reversal of 21333521 is 12533312.

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

It is a cyclic number.

It is not a de Polignac number, because 21333521 - 2²² = 17139217 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21333493 and 21333502.

It is not an unprimeable number, because it can be changed into a prime (21333511) 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, 56855 + ... + 57228.

It is an arithmetic number, because the mean of its divisors is an integer number (3080268).

Almost surely, 2^21333521 is an apocalyptic number.

It is an amenable number.

21333521 is a deficient number, since it is larger than the sum of its proper divisors (3308623).

21333521 is a wasteful number, since it uses less digits than its factorization.

21333521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114111.

The product of its digits is 540, while the sum is 20.

The square root of 21333521 is about 4618.8224689849. The cubic root of 21333521 is about 277.3453229929.

Adding to 21333521 its reverse (12533312), we get a palindrome (33866833).

The spelling of 21333521 in words is "twenty-one million, three hundred thirty-three thousand, five hundred twenty-one".