21520033 has 4 divisors (see below), whose sum is σ = 21565440. Its totient is φ = 21474628.

The previous prime is 21520021. The next prime is 21520061. The reversal of 21520033 is 33002512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21520033 is a prime.

It is a super-2 number, since 2×21520033² = 926223640642178, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21519989 and 21520016.

It is not an unprimeable number, because it can be changed into a prime (21520003) 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, 21985 + ... + 22942.

It is an arithmetic number, because the mean of its divisors is an integer number (5391360).

Almost surely, 2^21520033 is an apocalyptic number.

It is an amenable number.

21520033 is a deficient number, since it is larger than the sum of its proper divisors (45407).

21520033 is an equidigital number, since it uses as much as digits as its factorization.

21520033 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45406.

The product of its (nonzero) digits is 180, while the sum is 16.

The square root of 21520033 is about 4638.9689587235. The cubic root of 21520033 is about 278.1512254528.

Adding to 21520033 its reverse (33002512), we get a palindrome (54522545).

The spelling of 21520033 in words is "twenty-one million, five hundred twenty thousand, thirty-three".