21001233 has 16 divisors (see below), whose sum is σ = 30854592. Its totient is φ = 12600000.

The previous prime is 21001187. The next prime is 21001247. The reversal of 21001233 is 33210012.

It is a happy number.

It is not a de Polignac number, because 21001233 - 2⁸ = 21000977 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21001033) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 183 + ... + 6483.

It is an arithmetic number, because the mean of its divisors is an integer number (1928412).

Almost surely, 2^21001233 is an apocalyptic number.

It is an amenable number.

21001233 is a deficient number, since it is larger than the sum of its proper divisors (9853359).

21001233 is a wasteful number, since it uses less digits than its factorization.

21001233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6416.

The product of its (nonzero) digits is 36, while the sum is 12.

The square root of 21001233 is about 4582.7102243105. The cubic root of 21001233 is about 275.8978171412.

Adding to 21001233 its reverse (33210012), we get a palindrome (54211245).

It can be divided in two parts, 210012 and 33, that multiplied together give a palindrome (6930396).

The spelling of 21001233 in words is "twenty-one million, one thousand, two hundred thirty-three".