21609329 has 16 divisors (see below), whose sum is σ = 26396928. Its totient is φ = 17267712.

The previous prime is 21609293. The next prime is 21609373. The reversal of 21609329 is 92390612.

It is a de Polignac number, because none of the positive numbers 2^k-21609329 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21609295 and 21609304.

It is not an unprimeable number, because it can be changed into a prime (21609389) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12644 + ... + 14250.

It is an arithmetic number, because the mean of its divisors is an integer number (1649808).

Almost surely, 2^21609329 is an apocalyptic number.

It is an amenable number.

21609329 is a deficient number, since it is larger than the sum of its proper divisors (4787599).

21609329 is a wasteful number, since it uses less digits than its factorization.

21609329 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1744.

The product of its (nonzero) digits is 5832, while the sum is 32.

The square root of 21609329 is about 4648.5835477057. The cubic root of 21609329 is about 278.5354181184.

The spelling of 21609329 in words is "twenty-one million, six hundred nine thousand, three hundred twenty-nine".