1991151 has 6 divisors (see below), whose sum is σ = 2876120. Its totient is φ = 1327428.

The previous prime is 1991147. The next prime is 1991153. The reversal of 1991151 is 1511991.

It is not a de Polignac number, because 1991151 - 2² = 1991147 is a prime.

It is an Ulam number.

It is a Duffinian number.

1991151 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991153) 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, 110611 + ... + 110628.

2^1991151 is an apocalyptic number.

1991151 is a deficient number, since it is larger than the sum of its proper divisors (884969).

1991151 is a wasteful number, since it uses less digits than its factorization.

1991151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221245 (or 221242 counting only the distinct ones).

The product of its digits is 405, while the sum is 27.

The square root of 1991151 is about 1411.0815001268. The cubic root of 1991151 is about 125.8060129081.

The spelling of 1991151 in words is "one million, nine hundred ninety-one thousand, one hundred fifty-one".