991609841 has 2 divisors, whose sum is σ = 991609842. Its totient is φ = 991609840.

The previous prime is 991609837. The next prime is 991609859. The reversal of 991609841 is 148906199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 638320225 + 353289616 = 25265^2 + 18796^2 .

It is a cyclic number.

It is not a de Polignac number, because 991609841 - 2² = 991609837 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (991609891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495804920 + 495804921.

It is an arithmetic number, because the mean of its divisors is an integer number (495804921).

Almost surely, 2^991609841 is an apocalyptic number.

It is an amenable number.

991609841 is a deficient number, since it is larger than the sum of its proper divisors (1).

991609841 is an equidigital number, since it uses as much as digits as its factorization.

991609841 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 139968, while the sum is 47.

The square root of 991609841 is about 31489.8371065968. The cubic root of 991609841 is about 997.1954220290.

The spelling of 991609841 in words is "nine hundred ninety-one million, six hundred nine thousand, eight hundred forty-one".