661181 has 16 divisors (see below), whose sum is σ = 777600. Its totient is φ = 557568.

The previous prime is 661139. The next prime is 661183. The reversal of 661181 is 181166.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 661181 - 2⁶ = 661117 is a prime.

It is a super-2 number, since 2×661181² = 874320629522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 661181.

It is not an unprimeable number, because it can be changed into a prime (661183) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7385 + ... + 7473.

It is an arithmetic number, because the mean of its divisors is an integer number (48600).

2⁶⁶¹¹⁸¹ is an apocalyptic number.

It is an amenable number.

661181 is a deficient number, since it is larger than the sum of its proper divisors (116419).

661181 is a wasteful number, since it uses less digits than its factorization.

661181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148.

The product of its digits is 288, while the sum is 23.

The square root of 661181 is about 813.1303708508. The cubic root of 661181 is about 87.1177776846.

The spelling of 661181 in words is "six hundred sixty-one thousand, one hundred eighty-one".