18885971897581 has 4 divisors (see below), whose sum is σ = 18893721580732. Its totient is φ = 18878222214432.

The previous prime is 18885971897567. The next prime is 18885971897587. The reversal of 18885971897581 is 18579817958881.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18004831104100 + 881140793481 = 4243210^2 + 938691^2 .

It is a cyclic number.

It is not a de Polignac number, because 18885971897581 - 2²⁷ = 18885837679853 is a prime.

It is a super-2 number, since 2×18885971897581² (a number of 27 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 (18885971897587) 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, 3874837920 + ... + 3874842793.

It is an arithmetic number, because the mean of its divisors is an integer number (4723430395183).

Almost surely, 2^{18885971897581} is an apocalyptic number.

It is an amenable number.

18885971897581 is a deficient number, since it is larger than the sum of its proper divisors (7749683151).

18885971897581 is an equidigital number, since it uses as much as digits as its factorization.

18885971897581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7749683150.

The product of its digits is 3251404800, while the sum is 85.

The spelling of 18885971897581 in words is "eighteen trillion, eight hundred eighty-five billion, nine hundred seventy-one million, eight hundred ninety-seven thousand, five hundred eighty-one".