21668109 has 8 divisors (see below), whose sum is σ = 28932672. Its totient is φ = 14424480.

The previous prime is 21668107. The next prime is 21668111. The reversal of 21668109 is 90186612.

It is an interprime number because it is at equal distance from previous prime (21668107) and next prime (21668111).

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

It is not a de Polignac number, because 21668109 - 2¹ = 21668107 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 21668109.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668107) 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, 2632 + ... + 7089.

It is an arithmetic number, because the mean of its divisors is an integer number (3616584).

Almost surely, 2^21668109 is an apocalyptic number.

It is an amenable number.

21668109 is a deficient number, since it is larger than the sum of its proper divisors (7264563).

21668109 is an equidigital number, since it uses as much as digits as its factorization.

21668109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10467.

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 21668109 is about 4654.9016101310. The cubic root of 21668109 is about 278.7877395329.

The spelling of 21668109 in words is "twenty-one million, six hundred sixty-eight thousand, one hundred nine".