18821772181 has 8 divisors (see below), whose sum is σ = 19352840760. Its totient is φ = 18297220032.

The previous prime is 18821772161. The next prime is 18821772257. The reversal of 18821772181 is 18127712881.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2979522225 + 15842249956 = 54585^2 + 125866^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18821772181 - 2¹⁷ = 18821641109 is a prime.

It is a super-2 number, since 2×18821772181² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18821772121) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 1623250 + ... + 1634803.

It is an arithmetic number, because the mean of its divisors is an integer number (2419105095).

Almost surely, 2^18821772181 is an apocalyptic number.

It is an amenable number.

18821772181 is a deficient number, since it is larger than the sum of its proper divisors (531068579).

18821772181 is a wasteful number, since it uses less digits than its factorization.

18821772181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3258215.

The product of its digits is 100352, while the sum is 46.

The spelling of 18821772181 in words is "eighteen billion, eight hundred twenty-one million, seven hundred seventy-two thousand, one hundred eighty-one".