991603 has 2 divisors, whose sum is σ = 991604. Its totient is φ = 991602.

The previous prime is 991579. The next prime is 991607. The reversal of 991603 is 306199.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991603 - 2⁹ = 991091 is a prime.

991603 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (991607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495801 + 495802.

It is an arithmetic number, because the mean of its divisors is an integer number (495802).

2⁹⁹¹⁶⁰³ is an apocalyptic number.

991603 is a deficient number, since it is larger than the sum of its proper divisors (1).

991603 is an equidigital number, since it uses as much as digits as its factorization.

991603 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1458, while the sum is 28.

The square root of 991603 is about 995.7926490992. The cubic root of 991603 is about 99.7193128846.

The spelling of 991603 in words is "nine hundred ninety-one thousand, six hundred three".