21335209 has 8 divisors (see below), whose sum is σ = 24442880. Its totient is φ = 18242496.

The previous prime is 21335207. The next prime is 21335219. The reversal of 21335209 is 90253312.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21335209 - 2¹ = 21335207 is a prime.

It is a super-2 number, since 2×21335209² = 910382286147362, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21335207) 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 7 ways as a sum of consecutive naturals, for example, 489 + ... + 6550.

It is an arithmetic number, because the mean of its divisors is an integer number (3055360).

Almost surely, 2^21335209 is an apocalyptic number.

It is an amenable number.

21335209 is a deficient number, since it is larger than the sum of its proper divisors (3107671).

21335209 is an equidigital number, since it uses as much as digits as its factorization.

21335209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7479.

The product of its (nonzero) digits is 1620, while the sum is 25.

The square root of 21335209 is about 4619.0051959269. The cubic root of 21335209 is about 277.3526377185.

The spelling of 21335209 in words is "twenty-one million, three hundred thirty-five thousand, two hundred nine".