991709597 has 2 divisors, whose sum is σ = 991709598. Its totient is φ = 991709596.

The previous prime is 991709519. The next prime is 991709639. The reversal of 991709597 is 795907199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 915304516 + 76405081 = 30254^2 + 8741^2 .

It is a cyclic number.

It is not a de Polignac number, because 991709597 - 2²⁸ = 723274141 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991759597) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495854798 + 495854799.

It is an arithmetic number, because the mean of its divisors is an integer number (495854799).

Almost surely, 2^991709597 is an apocalyptic number.

It is an amenable number.

991709597 is a deficient number, since it is larger than the sum of its proper divisors (1).

991709597 is an equidigital number, since it uses as much as digits as its factorization.

991709597 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1607445, while the sum is 56.

The square root of 991709597 is about 31491.4210063630. The cubic root of 991709597 is about 997.2288602110.

The spelling of 991709597 in words is "nine hundred ninety-one million, seven hundred nine thousand, five hundred ninety-seven".