21171663 has 12 divisors (see below), whose sum is σ = 30621240.
Its totient is φ = 14096016.
The previous prime is 21171649. The next prime is 21171671. The reversal of 21171663 is 36617112.
It is not a de Polignac number, because 21171663 - 28 = 21171407 is a prime.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (21171673) 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 11 ways as a sum of consecutive naturals, for example, 12268 + ... + 13886.
It is an arithmetic number, because the mean of its divisors is an integer number (2551770).
Almost surely, 221171663 is an apocalyptic number.
21171663 is a deficient number, since it is larger than the sum of its proper divisors (9449577).
21171663 is a wasteful number, since it uses less digits than its factorization.
21171663 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 3078 (or 3075 counting only the distinct ones).
The product of its digits is 1512, while the sum is 27.
The square root of 21171663 is about 4601.2675427538.
The cubic root of 21171663 is about 276.6421327900.
Adding to 21171663 its reverse (36617112), we get a palindrome (57788775).
The spelling of 21171663 in words is "twenty-one million, one hundred seventy-one thousand, six hundred sixty-three".