21696409 has 8 divisors (see below), whose sum is σ = 25166528. Its totient is φ = 18318960.

The previous prime is 21696401. The next prime is 21696413. The reversal of 21696409 is 90469612.

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

It is a cyclic number.

It is not a de Polignac number, because 21696409 - 2³ = 21696401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21696401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22662 + ... + 23599.

It is an arithmetic number, because the mean of its divisors is an integer number (3145816).

Almost surely, 2^21696409 is an apocalyptic number.

It is an amenable number.

21696409 is a deficient number, since it is larger than the sum of its proper divisors (3470119).

21696409 is an equidigital number, since it uses as much as digits as its factorization.

21696409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46335.

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 21696409 is about 4657.9404246942. The cubic root of 21696409 is about 278.9090585444.

The spelling of 21696409 in words is "twenty-one million, six hundred ninety-six thousand, four hundred nine".