21108917 has 8 divisors (see below), whose sum is σ = 23322816. Its totient is φ = 19003072.

The previous prime is 21108911. The next prime is 21108929. The reversal of 21108917 is 71980112.

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 21108917 - 2¹⁶ = 21043381 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21108917.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21108911) 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, 26603 + ... + 27384.

It is an arithmetic number, because the mean of its divisors is an integer number (2915352).

Almost surely, 2^21108917 is an apocalyptic number.

It is an amenable number.

21108917 is a deficient number, since it is larger than the sum of its proper divisors (2213899).

21108917 is a wasteful number, since it uses less digits than its factorization.

21108917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54027.

The product of its (nonzero) digits is 1008, while the sum is 29.

The square root of 21108917 is about 4594.4441448341. Note that the first 3 decimals coincide. The cubic root of 21108917 is about 276.3685695909.

The spelling of 21108917 in words is "twenty-one million, one hundred eight thousand, nine hundred seventeen".