21000033 has 16 divisors (see below), whose sum is σ = 31391040. Its totient is φ = 13874112.

The previous prime is 20999999. The next prime is 21000037. The reversal of 21000033 is 33000012.

It is a happy number.

It is not a de Polignac number, because 21000033 - 2¹⁴ = 20983649 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

21000033 is a modest number, since divided by 33 gives 21 as remainder.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20999979 and 21000024.

It is not an unprimeable number, because it can be changed into a prime (21000037) 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 15 ways as a sum of consecutive naturals, for example, 391 + ... + 6492.

It is an arithmetic number, because the mean of its divisors is an integer number (1961940).

Almost surely, 2^21000033 is an apocalyptic number.

It is an amenable number.

21000033 is a deficient number, since it is larger than the sum of its proper divisors (10391007).

21000033 is a wasteful number, since it uses less digits than its factorization.

21000033 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7005 (or 6999 counting only the distinct ones).

The product of its (nonzero) digits is 18, while the sum is 9.

The square root of 21000033 is about 4582.5792955496. The cubic root of 21000033 is about 275.8925621531.

Adding to 21000033 its reverse (33000012), we get a palindrome (54000045).

The spelling of 21000033 in words is "twenty-one million, thirty-three", and thus it is an aban number and an uban number.