21004004521 has 2 divisors, whose sum is σ = 21004004522. Its totient is φ = 21004004520.

The previous prime is 21004004467. The next prime is 21004004531. The reversal of 21004004521 is 12540040012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10704799296 + 10299205225 = 103464^2 + 101485^2 .

It is a cyclic number.

It is not a de Polignac number, because 21004004521 - 2⁹ = 21004004009 is a prime.

It is not a weakly prime, because it can be changed into another prime (21004004531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502002260 + 10502002261.

It is an arithmetic number, because the mean of its divisors is an integer number (10502002261).

Almost surely, 2^21004004521 is an apocalyptic number.

It is an amenable number.

21004004521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004004521 is an equidigital number, since it uses as much as digits as its factorization.

21004004521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 320, while the sum is 19.

Adding to 21004004521 its reverse (12540040012), we get a palindrome (33544044533).

The spelling of 21004004521 in words is "twenty-one billion, four million, four thousand, five hundred twenty-one".