21633433621 has 2 divisors, whose sum is σ = 21633433622. Its totient is φ = 21633433620.

The previous prime is 21633433579. The next prime is 21633433667. The reversal of 21633433621 is 12633433612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18336951396 + 3296482225 = 135414^2 + 57415^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21633433621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21633433121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10816716810 + 10816716811.

It is an arithmetic number, because the mean of its divisors is an integer number (10816716811).

Almost surely, 2^21633433621 is an apocalyptic number.

It is an amenable number.

21633433621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21633433621 is an equidigital number, since it uses as much as digits as its factorization.

21633433621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 46656, while the sum is 34.

Subtracting from 21633433621 its reverse (12633433612), we obtain a palindrome (9000000009).

The spelling of 21633433621 in words is "twenty-one billion, six hundred thirty-three million, four hundred thirty-three thousand, six hundred twenty-one".