9921688057 has 2 divisors, whose sum is σ = 9921688058. Its totient is φ = 9921688056.

The previous prime is 9921688013. The next prime is 9921688061. The reversal of 9921688057 is 7508861299.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9592047721 + 329640336 = 97939^2 + 18156^2 .

It is an emirp because it is prime and its reverse (7508861299) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-9921688057 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 9921687989 and 9921688007.

It is not a weakly prime, because it can be changed into another prime (9921688157) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4960844028 + 4960844029.

It is an arithmetic number, because the mean of its divisors is an integer number (4960844029).

Almost surely, 2^9921688057 is an apocalyptic number.

It is an amenable number.

9921688057 is a deficient number, since it is larger than the sum of its proper divisors (1).

9921688057 is an equidigital number, since it uses as much as digits as its factorization.

9921688057 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2177280, while the sum is 55.

The square root of 9921688057 is about 99607.6706734978. The cubic root of 9921688057 is about 2148.7960129023.

The spelling of 9921688057 in words is "nine billion, nine hundred twenty-one million, six hundred eighty-eight thousand, fifty-seven".