21209433 has 16 divisors (see below), whose sum is σ = 32624640. Its totient is φ = 12005136.

The previous prime is 21209429. The next prime is 21209437. The reversal of 21209433 is 33490212.

It is an interprime number because it is at equal distance from previous prime (21209429) and next prime (21209437).

It is not a de Polignac number, because 21209433 - 2² = 21209429 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21209437) 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, 2473 + ... + 6966.

It is an arithmetic number, because the mean of its divisors is an integer number (2039040).

Almost surely, 2^21209433 is an apocalyptic number.

It is an amenable number.

21209433 is a deficient number, since it is larger than the sum of its proper divisors (11415207).

21209433 is a wasteful number, since it uses less digits than its factorization.

21209433 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9556.

The product of its (nonzero) digits is 1296, while the sum is 24.

The square root of 21209433 is about 4605.3700177076. The cubic root of 21209433 is about 276.8065438397.

Adding to 21209433 its reverse (33490212), we get a palindrome (54699645).

The spelling of 21209433 in words is "twenty-one million, two hundred nine thousand, four hundred thirty-three".