21724271 has 2 divisors, whose sum is σ = 21724272. Its totient is φ = 21724270.

The previous prime is 21724243. The next prime is 21724303. The reversal of 21724271 is 17242712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21724271 - 2⁶ = 21724207 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21724271.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21724231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10862135 + 10862136.

It is an arithmetic number, because the mean of its divisors is an integer number (10862136).

Almost surely, 2^21724271 is an apocalyptic number.

21724271 is a deficient number, since it is larger than the sum of its proper divisors (1).

21724271 is an equidigital number, since it uses as much as digits as its factorization.

21724271 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1568, while the sum is 26.

The square root of 21724271 is about 4660.9302719522. The cubic root of 21724271 is about 279.0283968818.

Adding to 21724271 its reverse (17242712), we get a palindrome (38966983).

The spelling of 21724271 in words is "twenty-one million, seven hundred twenty-four thousand, two hundred seventy-one".