21406937509 has 2 divisors, whose sum is σ = 21406937510. Its totient is φ = 21406937508.

The previous prime is 21406937477. The next prime is 21406937527. The reversal of 21406937509 is 90573960412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15586773409 + 5820164100 = 124847^2 + 76290^2 .

It is a cyclic number.

It is not a de Polignac number, because 21406937509 - 2⁵ = 21406937477 is a prime.

It is a super-2 number, since 2×21406937509² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21406937549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10703468754 + 10703468755.

It is an arithmetic number, because the mean of its divisors is an integer number (10703468755).

Almost surely, 2^21406937509 is an apocalyptic number.

It is an amenable number.

21406937509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21406937509 is an equidigital number, since it uses as much as digits as its factorization.

21406937509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 408240, while the sum is 46.

The spelling of 21406937509 in words is "twenty-one billion, four hundred six million, nine hundred thirty-seven thousand, five hundred nine".