21004089409 has 2 divisors, whose sum is σ = 21004089410. Its totient is φ = 21004089408.

The previous prime is 21004089397. The next prime is 21004089443. The reversal of 21004089409 is 90498040012.

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., 19193331600 + 1810757809 = 138540^2 + 42553^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21004089409 is a prime.

It is not a weakly prime, because it can be changed into another prime (21004089499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502044704 + 10502044705.

It is an arithmetic number, because the mean of its divisors is an integer number (10502044705).

Almost surely, 2^21004089409 is an apocalyptic number.

It is an amenable number.

21004089409 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004089409 is an equidigital number, since it uses as much as digits as its factorization.

21004089409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20736, while the sum is 37.

The spelling of 21004089409 in words is "twenty-one billion, four million, eighty-nine thousand, four hundred nine".