1991963 has 2 divisors, whose sum is σ = 1991964. Its totient is φ = 1991962.

The previous prime is 1991959. The next prime is 1991989. The reversal of 1991963 is 3691991.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1991963 - 2² = 1991959 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1991933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995981 + 995982.

It is an arithmetic number, because the mean of its divisors is an integer number (995982).

2^1991963 is an apocalyptic number.

1991963 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991963 is an equidigital number, since it uses as much as digits as its factorization.

1991963 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13122, while the sum is 38.

The square root of 1991963 is about 1411.3691933722. The cubic root of 1991963 is about 125.8231119962.

The spelling of 1991963 in words is "one million, nine hundred ninety-one thousand, nine hundred sixty-three".