21043523 has 2 divisors, whose sum is σ = 21043524. Its totient is φ = 21043522.

The previous prime is 21043499. The next prime is 21043543. The reversal of 21043523 is 32534012.

It is a happy number.

It is an a-pointer prime, because the next prime (21043543) can be obtained adding 21043523 to its sum of digits (20).

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21043523 - 2²⁴ = 4266307 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21043495 and 21043504.

It is not a weakly prime, because it can be changed into another prime (21043543) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521761 + 10521762.

It is an arithmetic number, because the mean of its divisors is an integer number (10521762).

Almost surely, 2^21043523 is an apocalyptic number.

21043523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21043523 is an equidigital number, since it uses as much as digits as its factorization.

21043523 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 21043523 is about 4587.3219856470. The cubic root of 21043523 is about 276.0828839848.

Adding to 21043523 its reverse (32534012), we get a palindrome (53577535).

The spelling of 21043523 in words is "twenty-one million, forty-three thousand, five hundred twenty-three".