181661436 has 72 divisors (see below), whose sum is σ = 507072384. Its totient is φ = 54375840.

The previous prime is 181661419. The next prime is 181661483. The reversal of 181661436 is 634166181.

181661436 is a `hidden beast` number, since 1 + 8 + 1 + 6 + 614 + 36 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 181661436.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 30105 + ... + 35631.

It is an arithmetic number, because the mean of its divisors is an integer number (7042672).

Almost surely, 2^181661436 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 181661436, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (253536192).

181661436 is an abundant number, since it is smaller than the sum of its proper divisors (325410948).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

181661436 is a wasteful number, since it uses less digits than its factorization.

181661436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5631 (or 5626 counting only the distinct ones).

The product of its digits is 20736, while the sum is 36.

The square root of 181661436 is about 13478.1837055295. The cubic root of 181661436 is about 566.3534898489.

The spelling of 181661436 in words is "one hundred eighty-one million, six hundred sixty-one thousand, four hundred thirty-six".