21699609 has 8 divisors (see below), whose sum is σ = 29013120. Its totient is φ = 14426256.

The previous prime is 21699607. The next prime is 21699617. The reversal of 21699609 is 90699612.

It is a happy number.

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

It is not a de Polignac number, because 21699609 - 2¹ = 21699607 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21699607) 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 7 ways as a sum of consecutive naturals, for example, 8754 + ... + 10955.

It is an arithmetic number, because the mean of its divisors is an integer number (3626640).

Almost surely, 2^21699609 is an apocalyptic number.

It is an amenable number.

21699609 is a deficient number, since it is larger than the sum of its proper divisors (7313511).

21699609 is a wasteful number, since it uses less digits than its factorization.

21699609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20079.

The product of its (nonzero) digits is 52488, while the sum is 42.

The square root of 21699609 is about 4658.2839114850. The cubic root of 21699609 is about 278.9227699550.

The spelling of 21699609 in words is "twenty-one million, six hundred ninety-nine thousand, six hundred nine".