21238543 has 2 divisors, whose sum is σ = 21238544. Its totient is φ = 21238542.

The previous prime is 21238519. The next prime is 21238549. The reversal of 21238543 is 34583212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21238543 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 (21238549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10619271 + 10619272.

It is an arithmetic number, because the mean of its divisors is an integer number (10619272).

Almost surely, 2^21238543 is an apocalyptic number.

21238543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21238543 is an equidigital number, since it uses as much as digits as its factorization.

21238543 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5760, while the sum is 28.

The square root of 21238543 is about 4608.5293749742. The cubic root of 21238543 is about 276.9331251716.

The spelling of 21238543 in words is "twenty-one million, two hundred thirty-eight thousand, five hundred forty-three".