21331023209 has 2 divisors, whose sum is σ = 21331023210. Its totient is φ = 21331023208.

The previous prime is 21331023191. The next prime is 21331023271. The reversal of 21331023209 is 90232013312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18823016809 + 2508006400 = 137197^2 + 50080^2 .

It is a cyclic number.

It is not a de Polignac number, because 21331023209 - 2¹² = 21331019113 is a prime.

It is a super-2 number, since 2×21331023209² (a number of 21 digits) contains 22 as substring.

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 (21331026209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10665511604 + 10665511605.

It is an arithmetic number, because the mean of its divisors is an integer number (10665511605).

Almost surely, 2^21331023209 is an apocalyptic number.

It is an amenable number.

21331023209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331023209 is an equidigital number, since it uses as much as digits as its factorization.

21331023209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 26.

The spelling of 21331023209 in words is "twenty-one billion, three hundred thirty-one million, twenty-three thousand, two hundred nine".