21609323 has 4 divisors (see below), whose sum is σ = 21747120. Its totient is φ = 21471528.

The previous prime is 21609293. The next prime is 21609373. The reversal of 21609323 is 32390612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21609323 - 2¹⁴ = 21592939 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21609292 and 21609301.

It is not an unprimeable number, because it can be changed into a prime (21609373) 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, 68663 + ... + 68976.

It is an arithmetic number, because the mean of its divisors is an integer number (5436780).

Almost surely, 2^21609323 is an apocalyptic number.

21609323 is a deficient number, since it is larger than the sum of its proper divisors (137797).

21609323 is a wasteful number, since it uses less digits than its factorization.

21609323 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137796.

The product of its (nonzero) digits is 1944, while the sum is 26.

The square root of 21609323 is about 4648.5829023478. The cubic root of 21609323 is about 278.5353923392.

Adding to 21609323 its reverse (32390612), we get a palindrome (53999935).

The spelling of 21609323 in words is "twenty-one million, six hundred nine thousand, three hundred twenty-three".