181688821 has 2 divisors, whose sum is σ = 181688822. Its totient is φ = 181688820.

The previous prime is 181688813. The next prime is 181688831. The reversal of 181688821 is 128886181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 179962225 + 1726596 = 13415^2 + 1314^2 .

It is a cyclic number.

It is not a de Polignac number, because 181688821 - 2³ = 181688813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181688831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90844410 + 90844411.

It is an arithmetic number, because the mean of its divisors is an integer number (90844411).

Almost surely, 2^181688821 is an apocalyptic number.

It is an amenable number.

181688821 is a deficient number, since it is larger than the sum of its proper divisors (1).

181688821 is an equidigital number, since it uses as much as digits as its factorization.

181688821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 49152, while the sum is 43.

The square root of 181688821 is about 13479.1995682236. The cubic root of 181688821 is about 566.3819472023.

The spelling of 181688821 in words is "one hundred eighty-one million, six hundred eighty-eight thousand, eight hundred twenty-one".