21688747541 has 2 divisors, whose sum is σ = 21688747542. Its totient is φ = 21688747540.

The previous prime is 21688747489. The next prime is 21688747631. The reversal of 21688747541 is 14574788612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21688747441 + 100 = 147271^2 + 10^2 .

It is a cyclic number.

It is not a de Polignac number, because 21688747541 - 2³⁰ = 20615005717 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21688747841) 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, 10844373770 + 10844373771.

It is an arithmetic number, because the mean of its divisors is an integer number (10844373771).

Almost surely, 2^21688747541 is an apocalyptic number.

It is an amenable number.

21688747541 is a deficient number, since it is larger than the sum of its proper divisors (1).

21688747541 is an equidigital number, since it uses as much as digits as its factorization.

21688747541 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3010560, while the sum is 53.

The spelling of 21688747541 in words is "twenty-one billion, six hundred eighty-eight million, seven hundred forty-seven thousand, five hundred forty-one".