21517888657 has 2 divisors, whose sum is σ = 21517888658. Its totient is φ = 21517888656.

The previous prime is 21517888631. The next prime is 21517888663. The reversal of 21517888657 is 75688871512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21431788816 + 86099841 = 146396^2 + 9279^2 .

It is a cyclic number.

It is not a de Polignac number, because 21517888657 - 2¹¹ = 21517886609 is a prime.

It is not a weakly prime, because it can be changed into another prime (21517888687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758944328 + 10758944329.

It is an arithmetic number, because the mean of its divisors is an integer number (10758944329).

Almost surely, 2^21517888657 is an apocalyptic number.

It is an amenable number.

21517888657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21517888657 is an equidigital number, since it uses as much as digits as its factorization.

21517888657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7526400, while the sum is 58.

The spelling of 21517888657 in words is "twenty-one billion, five hundred seventeen million, eight hundred eighty-eight thousand, six hundred fifty-seven".