21033605 has 4 divisors (see below), whose sum is σ = 25240332. Its totient is φ = 16826880.

The previous prime is 21033601. The next prime is 21033631. The reversal of 21033605 is 50633012.

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 7365796 + 13667809 = 2714^2 + 3697^2 .

It is not a de Polignac number, because 21033605 - 2² = 21033601 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21033601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2103356 + ... + 2103365.

It is an arithmetic number, because the mean of its divisors is an integer number (6310083).

Almost surely, 2^21033605 is an apocalyptic number.

It is an amenable number.

21033605 is a deficient number, since it is larger than the sum of its proper divisors (4206727).

21033605 is an equidigital number, since it uses as much as digits as its factorization.

21033605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4206726.

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

The square root of 21033605 is about 4586.2408353683. The cubic root of 21033605 is about 276.0395037274.

Adding to 21033605 its reverse (50633012), we get a palindrome (71666617).

The spelling of 21033605 in words is "twenty-one million, thirty-three thousand, six hundred five".