1021011991 has 2 divisors, whose sum is σ = 1021011992. Its totient is φ = 1021011990.

The previous prime is 1021011989. The next prime is 1021012033. The reversal of 1021011991 is 1991101201.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1021011991 - 2¹ = 1021011989 is a prime.

Together with 1021011989, 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 (1021011931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510505995 + 510505996.

It is an arithmetic number, because the mean of its divisors is an integer number (510505996).

Almost surely, 2^1021011991 is an apocalyptic number.

1021011991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1021011991 is an equidigital number, since it uses as much as digits as its factorization.

1021011991 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 25.

The square root of 1021011991 is about 31953.2782512217. The cubic root of 1021011991 is about 1006.9555057725.

It can be divided in two parts, 10210 and 11991, that added together give a square (22201 = 149²).

The spelling of 1021011991 in words is "one billion, twenty-one million, eleven thousand, nine hundred ninety-one".