1131581 has 4 divisors (see below), whose sum is σ = 1234464. Its totient is φ = 1028700.

The previous prime is 1131569. The next prime is 1131617. The reversal of 1131581 is 1851311.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1131581 - 2¹⁸ = 869437 is a prime.

It is a super-2 number, since 2×1131581² = 2560951119122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1131181) 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, 51425 + ... + 51446.

It is an arithmetic number, because the mean of its divisors is an integer number (308616).

2^1131581 is an apocalyptic number.

1131581 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1131581 is a deficient number, since it is larger than the sum of its proper divisors (102883).

1131581 is a wasteful number, since it uses less digits than its factorization.

1131581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102882.

The product of its digits is 120, while the sum is 20.

The square root of 1131581 is about 1063.7579611923. The cubic root of 1131581 is about 104.2065974556.

Adding to 1131581 its reverse (1851311), we get a palindrome (2982892).

The spelling of 1131581 in words is "one million, one hundred thirty-one thousand, five hundred eighty-one".