891581 has 4 divisors (see below), whose sum is σ = 893472. Its totient is φ = 889692.

The previous prime is 891577. The next prime is 891587. The reversal of 891581 is 185198.

It is a happy number.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 891581 - 2² = 891577 is a prime.

It is a super-2 number, since 2×891581² = 1589833359122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (891587) 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 3 ways as a sum of consecutive naturals, for example, 416 + ... + 1398.

It is an arithmetic number, because the mean of its divisors is an integer number (223368).

2⁸⁹¹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

891581 is a deficient number, since it is larger than the sum of its proper divisors (1891).

891581 is an equidigital number, since it uses as much as digits as its factorization.

891581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1890.

The product of its digits is 2880, while the sum is 32.

The square root of 891581 is about 944.2356697351. The cubic root of 891581 is about 96.2469409271.

The spelling of 891581 in words is "eight hundred ninety-one thousand, five hundred eighty-one".