21153309 has 4 divisors (see below), whose sum is σ = 28204416. Its totient is φ = 14102204.

The previous prime is 21153299. The next prime is 21153323. The reversal of 21153309 is 90335112.

It is a happy number.

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 21153309 - 2⁸ = 21153053 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21153359) 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 3 ways as a sum of consecutive naturals, for example, 3525549 + ... + 3525554.

It is an arithmetic number, because the mean of its divisors is an integer number (7051104).

Almost surely, 2^21153309 is an apocalyptic number.

It is an amenable number.

21153309 is a deficient number, since it is larger than the sum of its proper divisors (7051107).

21153309 is an equidigital number, since it uses as much as digits as its factorization.

21153309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7051106.

The product of its (nonzero) digits is 810, while the sum is 24.

The square root of 21153309 is about 4599.2726598887. The cubic root of 21153309 is about 276.5621680803.

The spelling of 21153309 in words is "twenty-one million, one hundred fifty-three thousand, three hundred nine".