21663271 has 8 divisors (see below), whose sum is σ = 25334144. Its totient is φ = 18136440.

The previous prime is 21663251. The next prime is 21663277. The reversal of 21663271 is 17236612.

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

It is not a de Polignac number, because 21663271 - 2¹¹ = 21661223 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663277) 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, 35685 + ... + 36286.

It is an arithmetic number, because the mean of its divisors is an integer number (3166768).

Almost surely, 2^21663271 is an apocalyptic number.

21663271 is a deficient number, since it is larger than the sum of its proper divisors (3670873).

21663271 is an equidigital number, since it uses as much as digits as its factorization.

21663271 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72021.

The product of its digits is 3024, while the sum is 28.

The square root of 21663271 is about 4654.3819138528. The cubic root of 21663271 is about 278.7669889838.

Adding to 21663271 its reverse (17236612), we get a palindrome (38899883).

The spelling of 21663271 in words is "twenty-one million, six hundred sixty-three thousand, two hundred seventy-one".