21153233 has 4 divisors (see below), whose sum is σ = 21724980. Its totient is φ = 20581488.

The previous prime is 21153227. The next prime is 21153257. The reversal of 21153233 is 33235112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17497489 + 3655744 = 4183^2 + 1912^2 .

It is a cyclic number.

It is not a de Polignac number, because 21153233 - 2¹⁴ = 21136849 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21153263) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 285818 + ... + 285891.

It is an arithmetic number, because the mean of its divisors is an integer number (5431245).

Almost surely, 2^21153233 is an apocalyptic number.

It is an amenable number.

21153233 is a deficient number, since it is larger than the sum of its proper divisors (571747).

21153233 is an equidigital number, since it uses as much as digits as its factorization.

21153233 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 571746.

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

The square root of 21153233 is about 4599.2643977054. The cubic root of 21153233 is about 276.5618368673.

Adding to 21153233 its reverse (33235112), we get a palindrome (54388345).

The spelling of 21153233 in words is "twenty-one million, one hundred fifty-three thousand, two hundred thirty-three".