1991001983 has 2 divisors, whose sum is σ = 1991001984. Its totient is φ = 1991001982.

The previous prime is 1991001977. The next prime is 1991002007. The reversal of 1991001983 is 3891001991.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (3891001991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1991001983 - 2⁴ = 1991001967 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1991001983.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991000983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995500991 + 995500992.

It is an arithmetic number, because the mean of its divisors is an integer number (995500992).

Almost surely, 2^1991001983 is an apocalyptic number.

1991001983 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991001983 is an equidigital number, since it uses as much as digits as its factorization.

1991001983 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17496, while the sum is 41.

The square root of 1991001983 is about 44620.6452553075. The cubic root of 1991001983 is about 1258.0287440470.

The spelling of 1991001983 in words is "one billion, nine hundred ninety-one million, one thousand, nine hundred eighty-three".