9921688157 has 2 divisors, whose sum is σ = 9921688158. Its totient is φ = 9921688156.

The previous prime is 9921688093. The next prime is 9921688159. The reversal of 9921688157 is 7518861299.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9818035396 + 103652761 = 99086^2 + 10181^2 .

It is a cyclic number.

It is not a de Polignac number, because 9921688157 - 2⁶ = 9921688093 is a prime.

Together with 9921688159, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9921688159) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4960844078 + 4960844079.

It is an arithmetic number, because the mean of its divisors is an integer number (4960844079).

Almost surely, 2^9921688157 is an apocalyptic number.

It is an amenable number.

9921688157 is a deficient number, since it is larger than the sum of its proper divisors (1).

9921688157 is an equidigital number, since it uses as much as digits as its factorization.

9921688157 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2177280, while the sum is 56.

The square root of 9921688157 is about 99607.6711754672. The cubic root of 9921688157 is about 2148.7960201215.

The spelling of 9921688157 in words is "nine billion, nine hundred twenty-one million, six hundred eighty-eight thousand, one hundred fifty-seven".