21523543 has 2 divisors, whose sum is σ = 21523544. Its totient is φ = 21523542.

The previous prime is 21523531. The next prime is 21523571. The reversal of 21523543 is 34532512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21523543 - 2⁵ = 21523511 is a prime.

It is a plaindrome in base 9.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21523573) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10761771 + 10761772.

It is an arithmetic number, because the mean of its divisors is an integer number (10761772).

Almost surely, 2^21523543 is an apocalyptic number.

21523543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21523543 is an equidigital number, since it uses as much as digits as its factorization.

21523543 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3600, while the sum is 25.

The square root of 21523543 is about 4639.3472601218. The cubic root of 21523543 is about 278.1663471416.

The spelling of 21523543 in words is "twenty-one million, five hundred twenty-three thousand, five hundred forty-three".