21718241 has 2 divisors, whose sum is σ = 21718242. Its totient is φ = 21718240.

The previous prime is 21718201. The next prime is 21718243. The reversal of 21718241 is 14281712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15241216 + 6477025 = 3904^2 + 2545^2 .

It is a cyclic number.

It is not a de Polignac number, because 21718241 - 2¹⁰ = 21717217 is a prime.

Together with 21718243, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21718241.

It is not a weakly prime, because it can be changed into another prime (21718243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10859120 + 10859121.

It is an arithmetic number, because the mean of its divisors is an integer number (10859121).

Almost surely, 2^21718241 is an apocalyptic number.

It is an amenable number.

21718241 is a deficient number, since it is larger than the sum of its proper divisors (1).

21718241 is an equidigital number, since it uses as much as digits as its factorization.

21718241 is an evil number, because the sum of its binary digits is even.

The product of its digits is 896, while the sum is 26.

The square root of 21718241 is about 4660.2833604836. The cubic root of 21718241 is about 279.0025778807.

Subtracting from 21718241 its product of digits (896), we obtain a triangular number (21717345 = T₆₅₉₀).

Adding to 21718241 its reverse (14281712), we get a palindrome (35999953).

Subtracting from 21718241 its reverse (14281712), we obtain a square (7436529 = 2727²).

The spelling of 21718241 in words is "twenty-one million, seven hundred eighteen thousand, two hundred forty-one".