21081233 has 4 divisors (see below), whose sum is σ = 21123648. Its totient is φ = 21038820.

The previous prime is 21081217. The next prime is 21081259. The reversal of 21081233 is 33218012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21081233 - 2⁴ = 21081217 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21081293) 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, 20453 + ... + 21458.

It is an arithmetic number, because the mean of its divisors is an integer number (5280912).

Almost surely, 2^21081233 is an apocalyptic number.

It is an amenable number.

21081233 is a deficient number, since it is larger than the sum of its proper divisors (42415).

21081233 is an equidigital number, since it uses as much as digits as its factorization.

21081233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42414.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21081233 is about 4591.4303871452. The cubic root of 21081233 is about 276.2476991134.

Adding to 21081233 its reverse (33218012), we get a palindrome (54299245).

The spelling of 21081233 in words is "twenty-one million, eighty-one thousand, two hundred thirty-three".