1020991 has 2 divisors, whose sum is σ = 1020992. Its totient is φ = 1020990.

The previous prime is 1020989. The next prime is 1020997. The reversal of 1020991 is 1990201.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1020991 - 2¹ = 1020989 is a prime.

Together with 1020989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1020997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510495 + 510496.

It is an arithmetic number, because the mean of its divisors is an integer number (510496).

2^1020991 is an apocalyptic number.

1020991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1020991 is an equidigital number, since it uses as much as digits as its factorization.

1020991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 162, while the sum is 22.

The square root of 1020991 is about 1010.4409928343. The cubic root of 1020991 is about 100.6948605054.

The spelling of 1020991 in words is "one million, twenty thousand, nine hundred ninety-one".