21242443 has 2 divisors, whose sum is σ = 21242444. Its totient is φ = 21242442.

The previous prime is 21242393. The next prime is 21242461. The reversal of 21242443 is 34424212.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21242443 is a prime.

It is not a weakly prime, because it can be changed into another prime (21246443) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621221 + 10621222.

It is an arithmetic number, because the mean of its divisors is an integer number (10621222).

Almost surely, 2^21242443 is an apocalyptic number.

21242443 is a deficient number, since it is larger than the sum of its proper divisors (1).

21242443 is an equidigital number, since it uses as much as digits as its factorization.

21242443 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1536, while the sum is 22.

The square root of 21242443 is about 4608.9524840250. The cubic root of 21242443 is about 276.9500750644.

Adding to 21242443 its reverse (34424212), we get a palindrome (55666655).

The spelling of 21242443 in words is "twenty-one million, two hundred forty-two thousand, four hundred forty-three".