21333421 has 4 divisors (see below), whose sum is σ = 21370972. Its totient is φ = 21295872.

The previous prime is 21333413. The next prime is 21333437. The reversal of 21333421 is 12433312.

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 14516100 + 6817321 = 3810^2 + 2611^2 .

It is a cyclic number.

It is not a de Polignac number, because 21333421 - 2³ = 21333413 is a prime.

It is a super-2 number, since 2×21333421² = 910229703126482, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21333451) 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, 17910 + ... + 19063.

It is an arithmetic number, because the mean of its divisors is an integer number (5342743).

Almost surely, 2^21333421 is an apocalyptic number.

It is an amenable number.

21333421 is a deficient number, since it is larger than the sum of its proper divisors (37551).

21333421 is an equidigital number, since it uses as much as digits as its factorization.

21333421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37550.

The product of its digits is 432, while the sum is 19.

The square root of 21333421 is about 4618.8116437023. The cubic root of 21333421 is about 277.3448896439.

Adding to 21333421 its reverse (12433312), we get a palindrome (33766733).

The spelling of 21333421 in words is "twenty-one million, three hundred thirty-three thousand, four hundred twenty-one".