21033421 has 8 divisors (see below), whose sum is σ = 21536280. Its totient is φ = 20534592.

The previous prime is 21033413. The next prime is 21033433. The reversal of 21033421 is 12433012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 9548100 + 11485321 = 3090^2 + 3389^2 .

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 21033421 - 2³ = 21033413 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21033395 and 21033404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21033401) 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, 11271 + ... + 13003.

It is an arithmetic number, because the mean of its divisors is an integer number (2692035).

Almost surely, 2^21033421 is an apocalyptic number.

It is an amenable number.

21033421 is a deficient number, since it is larger than the sum of its proper divisors (502859).

21033421 is a wasteful number, since it uses less digits than its factorization.

21033421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2015.

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21033421 is about 4586.2207753225. The cubic root of 21033421 is about 276.0386988025.

Adding to 21033421 its reverse (12433012), we get a palindrome (33466433).

The spelling of 21033421 in words is "twenty-one million, thirty-three thousand, four hundred twenty-one".