816181 has 4 divisors (see below), whose sum is σ = 824364. Its totient is φ = 808000.

The previous prime is 816169. The next prime is 816191. The reversal of 816181 is 181618.

It is a happy number.

816181 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 576081 + 240100 = 759^2 + 490^2 .

It is not a de Polignac number, because 816181 - 2⁹ = 815669 is a prime.

It is a super-4 number, since 4×816181⁴ (a number of 25 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

816181 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816121) 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, 3940 + ... + 4141.

It is an arithmetic number, because the mean of its divisors is an integer number (206091).

2⁸¹⁶¹⁸¹ is an apocalyptic number.

It is an amenable number.

816181 is a deficient number, since it is larger than the sum of its proper divisors (8183).

816181 is a wasteful number, since it uses less digits than its factorization.

816181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8182.

The product of its digits is 384, while the sum is 25.

The square root of 816181 is about 903.4273628798. The cubic root of 816181 is about 93.4534833006.

Adding to 816181 its reverse (181618), we get a palindrome (997799).

It can be divided in two parts, 816 and 181, that multiplied together give a triangular number (147696 = T₅₄₃).

The spelling of 816181 in words is "eight hundred sixteen thousand, one hundred eighty-one".