21159609 has 8 divisors (see below), whose sum is σ = 29439552. Its totient is φ = 13493040.

The previous prime is 21159587. The next prime is 21159613. The reversal of 21159609 is 90695112.

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

It is not a de Polignac number, because 21159609 - 2¹² = 21155513 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21159609.

It is not an unprimeable number, because it can be changed into a prime (21159629) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 153262 + ... + 153399.

It is an arithmetic number, because the mean of its divisors is an integer number (3679944).

Almost surely, 2^21159609 is an apocalyptic number.

It is an amenable number.

21159609 is a deficient number, since it is larger than the sum of its proper divisors (8279943).

21159609 is a wasteful number, since it uses less digits than its factorization.

21159609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 306687.

The product of its (nonzero) digits is 4860, while the sum is 33.

The square root of 21159609 is about 4599.9574998037. The cubic root of 21159609 is about 276.5896211329.

The spelling of 21159609 in words is "twenty-one million, one hundred fifty-nine thousand, six hundred nine".