21618241 has 2 divisors, whose sum is σ = 21618242. Its totient is φ = 21618240.

The previous prime is 21618227. The next prime is 21618251. The reversal of 21618241 is 14281612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20214016 + 1404225 = 4496^2 + 1185^2 .

It is a cyclic number.

It is not a de Polignac number, because 21618241 - 2⁵ = 21618209 is a prime.

It is not a weakly prime, because it can be changed into another prime (21618221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10809120 + 10809121.

It is an arithmetic number, because the mean of its divisors is an integer number (10809121).

Almost surely, 2^21618241 is an apocalyptic number.

It is an amenable number.

21618241 is a deficient number, since it is larger than the sum of its proper divisors (1).

21618241 is an equidigital number, since it uses as much as digits as its factorization.

21618241 is an evil number, because the sum of its binary digits is even.

The product of its digits is 768, while the sum is 25.

The square root of 21618241 is about 4649.5420204575. The cubic root of 21618241 is about 278.5737035348.

Adding to 21618241 its reverse (14281612), we get a palindrome (35899853).

The spelling of 21618241 in words is "twenty-one million, six hundred eighteen thousand, two hundred forty-one".