21231271 has 4 divisors (see below), whose sum is σ = 21272544. Its totient is φ = 21190000.

The previous prime is 21231269. The next prime is 21231307. The reversal of 21231271 is 17213212.

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 21231271 - 2¹ = 21231269 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 (21231241) 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, 19855 + ... + 20896.

It is an arithmetic number, because the mean of its divisors is an integer number (5318136).

Almost surely, 2^21231271 is an apocalyptic number.

21231271 is a deficient number, since it is larger than the sum of its proper divisors (41273).

21231271 is an equidigital number, since it uses as much as digits as its factorization.

21231271 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41272.

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

The square root of 21231271 is about 4607.7403355658. The cubic root of 21231271 is about 276.9015145980.

Adding to 21231271 its reverse (17213212), we get a palindrome (38444483).

The spelling of 21231271 in words is "twenty-one million, two hundred thirty-one thousand, two hundred seventy-one".