21541543 has 2 divisors, whose sum is σ = 21541544. Its totient is φ = 21541542.

The previous prime is 21541537. The next prime is 21541589. The reversal of 21541543 is 34514512.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21541543 - 2¹⁷ = 21410471 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21541043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770771 + 10770772.

It is an arithmetic number, because the mean of its divisors is an integer number (10770772).

Almost surely, 2^21541543 is an apocalyptic number.

21541543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21541543 is an equidigital number, since it uses as much as digits as its factorization.

21541543 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2400, while the sum is 25.

The square root of 21541543 is about 4641.2867827791. The cubic root of 21541543 is about 278.2438684419.

The spelling of 21541543 in words is "twenty-one million, five hundred forty-one thousand, five hundred forty-three".