1991329 has 8 divisors (see below), whose sum is σ = 2160648. Its totient is φ = 1827840.

The previous prime is 1991293. The next prime is 1991351. The reversal of 1991329 is 9231991.

It can be written as a sum of positive squares in 4 ways, for example, as 230400 + 1760929 = 480^2 + 1327^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-1991329 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1991294 and 1991303.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991359) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 732 + ... + 2125.

It is an arithmetic number, because the mean of its divisors is an integer number (270081).

2^1991329 is an apocalyptic number.

It is an amenable number.

1991329 is a deficient number, since it is larger than the sum of its proper divisors (169319).

1991329 is a wasteful number, since it uses less digits than its factorization.

1991329 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2915.

The product of its digits is 4374, while the sum is 34.

The square root of 1991329 is about 1411.1445709069. The cubic root of 1991329 is about 125.8097616281.

The spelling of 1991329 in words is "one million, nine hundred ninety-one thousand, three hundred twenty-nine".