1328991 has 4 divisors (see below), whose sum is σ = 1771992. Its totient is φ = 885992.

The previous prime is 1328981. The next prime is 1329011. The reversal of 1328991 is 1998231.

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 1328991 - 2⁶ = 1328927 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1328911) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 221496 + ... + 221501.

It is an arithmetic number, because the mean of its divisors is an integer number (442998).

2^1328991 is an apocalyptic number.

1328991 is a deficient number, since it is larger than the sum of its proper divisors (443001).

1328991 is an equidigital number, since it uses as much as digits as its factorization.

1328991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 443000.

The product of its digits is 3888, while the sum is 33.

The square root of 1328991 is about 1152.8187194872. The cubic root of 1328991 is about 109.9446277786.

The spelling of 1328991 in words is "one million, three hundred twenty-eight thousand, nine hundred ninety-one".