21216271 has 4 divisors (see below), whose sum is σ = 21616632. Its totient is φ = 20815912.

The previous prime is 21216263. The next prime is 21216361. The reversal of 21216271 is 17261212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21216271 - 2³ = 21216263 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216241) 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 3 ways as a sum of consecutive naturals, for example, 200101 + ... + 200206.

It is an arithmetic number, because the mean of its divisors is an integer number (5404158).

Almost surely, 2^21216271 is an apocalyptic number.

21216271 is a deficient number, since it is larger than the sum of its proper divisors (400361).

21216271 is an equidigital number, since it uses as much as digits as its factorization.

21216271 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400360.

The product of its digits is 336, while the sum is 22.

The square root of 21216271 is about 4606.1123520817. The cubic root of 21216271 is about 276.8362884627.

Adding to 21216271 its reverse (17261212), we get a palindrome (38477483).

The spelling of 21216271 in words is "twenty-one million, two hundred sixteen thousand, two hundred seventy-one".