1991358 has 16 divisors (see below), whose sum is σ = 4425360. Its totient is φ = 663768.

The previous prime is 1991357. The next prime is 1991359. The reversal of 1991358 is 8531991.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1991357) and next prime (1991359).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991351) 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 7 ways as a sum of consecutive naturals, for example, 18385 + ... + 18492.

It is an arithmetic number, because the mean of its divisors is an integer number (276585).

2^1991358 is an apocalyptic number.

1991358 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1991358 is an abundant number, since it is smaller than the sum of its proper divisors (2434002).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1991358 is a wasteful number, since it uses less digits than its factorization.

1991358 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36888 (or 36882 counting only the distinct ones).

The product of its digits is 9720, while the sum is 36.

The square root of 1991358 is about 1411.1548462164. The cubic root of 1991358 is about 125.8103723535.

The spelling of 1991358 in words is "one million, nine hundred ninety-one thousand, three hundred fifty-eight".