21717871 has 8 divisors (see below), whose sum is σ = 24948000. Its totient is φ = 18519648.

The previous prime is 21717827. The next prime is 21717907. The reversal of 21717871 is 17871712.

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

It is not a de Polignac number, because 21717871 - 2¹¹ = 21715823 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21717071) 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, 6496 + ... + 9253.

It is an arithmetic number, because the mean of its divisors is an integer number (3118500).

Almost surely, 2^21717871 is an apocalyptic number.

21717871 is a deficient number, since it is larger than the sum of its proper divisors (3230129).

21717871 is a wasteful number, since it uses less digits than its factorization.

21717871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15953.

The product of its digits is 5488, while the sum is 34.

The square root of 21717871 is about 4660.2436631575. The cubic root of 21717871 is about 279.0009934746. Note that the first 3 decimals are identical.

The spelling of 21717871 in words is "twenty-one million, seven hundred seventeen thousand, eight hundred seventy-one".