21333333 has 32 divisors (see below), whose sum is σ = 34570240. Its totient is φ = 11430720.

The previous prime is 21333329. The next prime is 21333353. The reversal of 21333333 is 33333312.

It is not a de Polignac number, because 21333333 - 2² = 21333329 is a prime.

It is a super-2 number, since 2×21333333² = 910222193777778, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

21333333 is a modest number, since divided by 3333 gives 2133 as remainder.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21333353) 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 31 ways as a sum of consecutive naturals, for example, 50463 + ... + 50883.

It is an arithmetic number, because the mean of its divisors is an integer number (1080320).

Almost surely, 2^21333333 is an apocalyptic number.

21333333 is the 2667-th octagonal number.

It is an amenable number.

21333333 is a deficient number, since it is larger than the sum of its proper divisors (13236907).

21333333 is a wasteful number, since it uses less digits than its factorization.

21333333 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 577.

The product of its digits is 1458, while the sum is 21.

The square root of 21333333 is about 4618.8021174326. The cubic root of 21333333 is about 277.3445082958.

Subtracting from 21333333 its sum of digits (21), we obtain a palindrome (21333312).

Adding to 21333333 its reverse (33333312), we get a palindrome (54666645).

The spelling of 21333333 in words is "twenty-one million, three hundred thirty-three thousand, three hundred thirty-three".