18195581881 has 9 divisors (see below), whose sum is σ = 18634515951. Its totient is φ = 17766763392.

The previous prime is 18195581861. The next prime is 18195581891. The reversal of 18195581881 is 18818559181.

It is a happy number.

The square root of 18195581881 is 134891.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 18172388025 + 23193856 = 134805^2 + 4816^2 .

It is not a de Polignac number, because 18195581881 - 2¹¹ = 18195579833 is a prime.

It is a super-2 number, since 2×18195581881² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18195581861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 5798745 + ... + 5801881.

Almost surely, 2^18195581881 is an apocalyptic number.

18195581881 is the 134891-st square number.

18195581881 is the 67446-th centered octagonal number.

It is an amenable number.

18195581881 is a deficient number, since it is larger than the sum of its proper divisors (438934070).

18195581881 is an frugal number, since it uses more digits than its factorization.

18195581881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6360 (or 3180 counting only the distinct ones).

The product of its digits is 921600, while the sum is 55.

The spelling of 18195581881 in words is "eighteen billion, one hundred ninety-five million, five hundred eighty-one thousand, eight hundred eighty-one".