21243524509 has 2 divisors, whose sum is σ = 21243524510. Its totient is φ = 21243524508.

The previous prime is 21243524459. The next prime is 21243524527. The reversal of 21243524509 is 90542534212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15314062500 + 5929462009 = 123750^2 + 77003^2 .

It is a cyclic number.

It is not a de Polignac number, because 21243524509 - 2¹⁵ = 21243491741 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21243524539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621762254 + 10621762255.

It is an arithmetic number, because the mean of its divisors is an integer number (10621762255).

Almost surely, 2^21243524509 is an apocalyptic number.

It is an amenable number.

21243524509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243524509 is an equidigital number, since it uses as much as digits as its factorization.

21243524509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 86400, while the sum is 37.

The spelling of 21243524509 in words is "twenty-one billion, two hundred forty-three million, five hundred twenty-four thousand, five hundred nine".