21520404233 has 2 divisors, whose sum is σ = 21520404234. Its totient is φ = 21520404232.

The previous prime is 21520404229. The next prime is 21520404263. The reversal of 21520404233 is 33240402512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19599160009 + 1921244224 = 139997^2 + 43832^2 .

It is a cyclic number.

It is not a de Polignac number, because 21520404233 - 2² = 21520404229 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21520404223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760202116 + 10760202117.

It is an arithmetic number, because the mean of its divisors is an integer number (10760202117).

Almost surely, 2^21520404233 is an apocalyptic number.

It is an amenable number.

21520404233 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520404233 is an equidigital number, since it uses as much as digits as its factorization.

21520404233 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5760, while the sum is 26.

Adding to 21520404233 its reverse (33240402512), we get a palindrome (54760806745).

The spelling of 21520404233 in words is "twenty-one billion, five hundred twenty million, four hundred four thousand, two hundred thirty-three".