1018991 has 4 divisors (see below), whose sum is σ = 1031352. Its totient is φ = 1006632.

The previous prime is 1018987. The next prime is 1018993. The reversal of 1018991 is 1998101.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1018991 - 2² = 1018987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1018993) 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 in 3 ways as a sum of consecutive naturals, for example, 6056 + ... + 6221.

It is an arithmetic number, because the mean of its divisors is an integer number (257838).

2^1018991 is an apocalyptic number.

1018991 is a deficient number, since it is larger than the sum of its proper divisors (12361).

1018991 is an equidigital number, since it uses as much as digits as its factorization.

1018991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12360.

The product of its (nonzero) digits is 648, while the sum is 29.

The square root of 1018991 is about 1009.4508408040. The cubic root of 1018991 is about 100.6290677728.

The spelling of 1018991 in words is "one million, eighteen thousand, nine hundred ninety-one".