21218143 has 2 divisors, whose sum is σ = 21218144. Its totient is φ = 21218142.

The previous prime is 21218089. The next prime is 21218161. The reversal of 21218143 is 34181212.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21218143 - 2⁹ = 21217631 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21218173) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10609071 + 10609072.

It is an arithmetic number, because the mean of its divisors is an integer number (10609072).

Almost surely, 2^21218143 is an apocalyptic number.

21218143 is a deficient number, since it is larger than the sum of its proper divisors (1).

21218143 is an equidigital number, since it uses as much as digits as its factorization.

21218143 is an evil number, because the sum of its binary digits is even.

The product of its digits is 384, while the sum is 22.

The square root of 21218143 is about 4606.3155558429. The cubic root of 21218143 is about 276.8444303630.

Adding to 21218143 its reverse (34181212), we get a palindrome (55399355).

The spelling of 21218143 in words is "twenty-one million, two hundred eighteen thousand, one hundred forty-three".