1157991 has 4 divisors (see below), whose sum is σ = 1543992. Its totient is φ = 771992.

The previous prime is 1157987. The next prime is 1158007. The reversal of 1157991 is 1997511.

It is a happy number.

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 1157991 - 2² = 1157987 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 (1157491) 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, 192996 + ... + 193001.

It is an arithmetic number, because the mean of its divisors is an integer number (385998).

2^1157991 is an apocalyptic number.

1157991 is a deficient number, since it is larger than the sum of its proper divisors (386001).

1157991 is an equidigital number, since it uses as much as digits as its factorization.

1157991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386000.

The product of its digits is 2835, while the sum is 33.

The square root of 1157991 is about 1076.0999024254. The cubic root of 1157991 is about 105.0110645936.

The spelling of 1157991 in words is "one million, one hundred fifty-seven thousand, nine hundred ninety-one".