21033404521 has 2 divisors, whose sum is σ = 21033404522. Its totient is φ = 21033404520.

The previous prime is 21033404477. The next prime is 21033404531. The reversal of 21033404521 is 12540433012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15854587225 + 5178817296 = 125915^2 + 71964^2 .

It is a cyclic number.

It is not a de Polignac number, because 21033404521 - 2¹⁷ = 21033273449 is a prime.

It is not a weakly prime, because it can be changed into another prime (21033404531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10516702260 + 10516702261.

It is an arithmetic number, because the mean of its divisors is an integer number (10516702261).

Almost surely, 2^21033404521 is an apocalyptic number.

It is an amenable number.

21033404521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21033404521 is an equidigital number, since it uses as much as digits as its factorization.

21033404521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2880, while the sum is 25.

Adding to 21033404521 its reverse (12540433012), we get a palindrome (33573837533).

The spelling of 21033404521 in words is "twenty-one billion, thirty-three million, four hundred four thousand, five hundred twenty-one".