9991920997 has 2 divisors, whose sum is σ = 9991920998. Its totient is φ = 9991920996.

The previous prime is 9991920943. The next prime is 9991921033. The reversal of 9991920997 is 7990291999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5264808481 + 4727112516 = 72559^2 + 68754^2 .

It is a cyclic number.

It is not a de Polignac number, because 9991920997 - 2²³ = 9983532389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (9991924997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4995960498 + 4995960499.

It is an arithmetic number, because the mean of its divisors is an integer number (4995960499).

Almost surely, 2^9991920997 is an apocalyptic number.

It is an amenable number.

9991920997 is a deficient number, since it is larger than the sum of its proper divisors (1).

9991920997 is an equidigital number, since it uses as much as digits as its factorization.

9991920997 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7440174, while the sum is 64.

The square root of 9991920997 is about 99959.5968229164. The cubic root of 9991920997 is about 2153.8543442392.

The spelling of 9991920997 in words is "nine billion, nine hundred ninety-one million, nine hundred twenty thousand, nine hundred ninety-seven".