1991268 has 18 divisors (see below), whose sum is σ = 5033574. Its totient is φ = 663744.

The previous prime is 1991267. The next prime is 1991279. The reversal of 1991268 is 8621991.

It can be written as a sum of positive squares in only one way, i.e., 1954404 + 36864 = 1398^2 + 192^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 55313 = 1991268 / (1 + 9 + 9 + 1 + 2 + 6 + 8).

It is not an unprimeable number, because it can be changed into a prime (1991267) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 27621 + ... + 27692.

It is an arithmetic number, because the mean of its divisors is an integer number (279643).

2^1991268 is an apocalyptic number.

1991268 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

1991268 is an abundant number, since it is smaller than the sum of its proper divisors (3042306).

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

1991268 is a wasteful number, since it uses less digits than its factorization.

1991268 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55323 (or 55318 counting only the distinct ones).

The product of its digits is 7776, while the sum is 36.

The square root of 1991268 is about 1411.1229570806. The cubic root of 1991268 is about 125.8084769795.

The spelling of 1991268 in words is "one million, nine hundred ninety-one thousand, two hundred sixty-eight".