991920497 has 2 divisors, whose sum is σ = 991920498. Its totient is φ = 991920496.

The previous prime is 991920463. The next prime is 991920511. The reversal of 991920497 is 794029199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 845123041 + 146797456 = 29071^2 + 12116^2 .

It is a cyclic number.

It is not a de Polignac number, because 991920497 - 2¹⁰ = 991919473 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (991920407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495960248 + 495960249.

It is an arithmetic number, because the mean of its divisors is an integer number (495960249).

Almost surely, 2^991920497 is an apocalyptic number.

It is an amenable number.

991920497 is a deficient number, since it is larger than the sum of its proper divisors (1).

991920497 is an equidigital number, since it uses as much as digits as its factorization.

991920497 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 367416, while the sum is 50.

The square root of 991920497 is about 31494.7693593714. The cubic root of 991920497 is about 997.2995464483.

The spelling of 991920497 in words is "nine hundred ninety-one million, nine hundred twenty thousand, four hundred ninety-seven".