21252321 has 8 divisors (see below), whose sum is σ = 31484960. Its totient is φ = 14168196.

The previous prime is 21252293. The next prime is 21252323. The reversal of 21252321 is 12325212.

It is not a de Polignac number, because 21252321 - 2⁵ = 21252289 is a prime.

It is a super-2 number, since 2×21252321² = 903322295774082, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21252294 and 21252303.

It is not an unprimeable number, because it can be changed into a prime (21252323) 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, 393535 + ... + 393588.

It is an arithmetic number, because the mean of its divisors is an integer number (3935620).

Almost surely, 2^21252321 is an apocalyptic number.

It is an amenable number.

21252321 is a deficient number, since it is larger than the sum of its proper divisors (10232639).

21252321 is an equidigital number, since it uses as much as digits as its factorization.

21252321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 787132 (or 787126 counting only the distinct ones).

The product of its digits is 240, while the sum is 18.

The square root of 21252321 is about 4610.0239695689. The cubic root of 21252321 is about 276.9929968210.

Adding to 21252321 its reverse (12325212), we get a palindrome (33577533).

The spelling of 21252321 in words is "twenty-one million, two hundred fifty-two thousand, three hundred twenty-one".