181696721 has 4 divisors (see below), whose sum is σ = 182203200. Its totient is φ = 181190244.

The previous prime is 181696717. The next prime is 181696727. The reversal of 181696721 is 127696181.

181696721 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, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 127696181 = 41 ⋅3114541.

It is a cyclic number.

It is not a de Polignac number, because 181696721 - 2² = 181696717 is a prime.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (181696727) 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, 252701 + ... + 253418.

It is an arithmetic number, because the mean of its divisors is an integer number (45550800).

Almost surely, 2^181696721 is an apocalyptic number.

It is an amenable number.

181696721 is a deficient number, since it is larger than the sum of its proper divisors (506479).

181696721 is an equidigital number, since it uses as much as digits as its factorization.

181696721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 506478.

The product of its digits is 36288, while the sum is 41.

The square root of 181696721 is about 13479.4926091452. The cubic root of 181696721 is about 566.3901560224.

The spelling of 181696721 in words is "one hundred eighty-one million, six hundred ninety-six thousand, seven hundred twenty-one".