21353609 has 4 divisors (see below), whose sum is σ = 21465600. Its totient is φ = 21241620.

The previous prime is 21353603. The next prime is 21353611. The reversal of 21353609 is 90635312.

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 21353609 - 2⁴ = 21353593 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 (21353603) 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, 55709 + ... + 56090.

It is an arithmetic number, because the mean of its divisors is an integer number (5366400).

Almost surely, 2^21353609 is an apocalyptic number.

It is an amenable number.

21353609 is a deficient number, since it is larger than the sum of its proper divisors (111991).

21353609 is a wasteful number, since it uses less digits than its factorization.

21353609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111990.

The product of its (nonzero) digits is 4860, while the sum is 29.

The square root of 21353609 is about 4620.9965375447. The cubic root of 21353609 is about 277.4323466817.

The spelling of 21353609 in words is "twenty-one million, three hundred fifty-three thousand, six hundred nine".