21213271 has 4 divisors (see below), whose sum is σ = 21259552. Its totient is φ = 21166992.

The previous prime is 21213251. The next prime is 21213287. The reversal of 21213271 is 17231212.

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 21213271 - 2¹⁷ = 21082199 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 (21213251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22446 + ... + 23371.

It is an arithmetic number, because the mean of its divisors is an integer number (5314888).

Almost surely, 2^21213271 is an apocalyptic number.

21213271 is a deficient number, since it is larger than the sum of its proper divisors (46281).

21213271 is an equidigital number, since it uses as much as digits as its factorization.

21213271 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46280.

The product of its digits is 168, while the sum is 19.

The square root of 21213271 is about 4605.7866863327. The cubic root of 21213271 is about 276.8232395467.

Adding to 21213271 its reverse (17231212), we get a palindrome (38444483).

The spelling of 21213271 in words is "twenty-one million, two hundred thirteen thousand, two hundred seventy-one".