1002001991 has 2 divisors, whose sum is σ = 1002001992. Its totient is φ = 1002001990.

The previous prime is 1002001963. The next prime is 1002002009. The reversal of 1002001991 is 1991002001.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1002001991 - 2⁶ = 1002001927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1002000991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 501000995 + 501000996.

It is an arithmetic number, because the mean of its divisors is an integer number (501000996).

Almost surely, 2^1002001991 is an apocalyptic number.

1002001991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1002001991 is an equidigital number, since it uses as much as digits as its factorization.

1002001991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 162, while the sum is 23.

The square root of 1002001991 is about 31654.4150317140. The cubic root of 1002001991 is about 1000.6668854982. Note that the first 3 decimals are identical.

Adding to 1002001991 its reverse (1991002001), we get a palindrome (2993003992).

The spelling of 1002001991 in words is "one billion, two million, one thousand, nine hundred ninety-one".