21023604509 has 2 divisors, whose sum is σ = 21023604510. Its totient is φ = 21023604508.

The previous prime is 21023604493. The next prime is 21023604529. The reversal of 21023604509 is 90540632012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16745136409 + 4278468100 = 129403^2 + 65410^2 .

It is a cyclic number.

It is not a de Polignac number, because 21023604509 - 2⁴ = 21023604493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21023604529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10511802254 + 10511802255.

It is an arithmetic number, because the mean of its divisors is an integer number (10511802255).

Almost surely, 2^21023604509 is an apocalyptic number.

It is an amenable number.

21023604509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21023604509 is an equidigital number, since it uses as much as digits as its factorization.

21023604509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 32.

The spelling of 21023604509 in words is "twenty-one billion, twenty-three million, six hundred four thousand, five hundred nine".