851581 has 4 divisors (see below), whose sum is σ = 901692. Its totient is φ = 801472.

The previous prime is 851573. The next prime is 851597. The reversal of 851581 is 185158.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 302500 + 549081 = 550^2 + 741^2 .

It is a cyclic number.

It is not a de Polignac number, because 851581 - 2³ = 851573 is a prime.

It is a super-2 number, since 2×851581² = 1450380399122, which contains 22 as substring.

It is a Duffinian number.

851581 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (851381) 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, 25030 + ... + 25063.

It is an arithmetic number, because the mean of its divisors is an integer number (225423).

2⁸⁵¹⁵⁸¹ is an apocalyptic number.

It is an amenable number.

851581 is a deficient number, since it is larger than the sum of its proper divisors (50111).

851581 is a wasteful number, since it uses less digits than its factorization.

851581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50110.

The product of its digits is 1600, while the sum is 28.

The square root of 851581 is about 922.8114650350. The cubic root of 851581 is about 94.7855179739.

The spelling of 851581 in words is "eight hundred fifty-one thousand, five hundred eighty-one".