18168613681 has 9 divisors (see below), whose sum is σ = 18678055851. Its totient is φ = 17672717592.

The previous prime is 18168613669. The next prime is 18168613693. The reversal of 18168613681 is 18631686181.

It is a happy number.

The square root of 18168613681 is 134791.

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

It is an interprime number because it is at equal distance from previous prime (18168613669) and next prime (18168613693).

It can be written as a sum of positive squares in only one way, i.e., 16257525025 + 1911088656 = 127505^2 + 43716^2 .

It is not a de Polignac number, because 18168613681 - 2⁵ = 18168613649 is a prime.

It is a super-2 number, since 2×18168613681² (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 (18168613601) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 4985446 + ... + 4989088.

It is an arithmetic number, because the mean of its divisors is an integer number (2075339539).

Almost surely, 2^18168613681 is an apocalyptic number.

18168613681 is the 134791-st square number.

18168613681 is the 67396-th centered octagonal number.

It is an amenable number.

18168613681 is a deficient number, since it is larger than the sum of its proper divisors (509442170).

18168613681 is an frugal number, since it uses more digits than its factorization.

18168613681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7360 (or 3680 counting only the distinct ones).

The product of its digits is 331776, while the sum is 49.

Multiplying 18168613681 by its sum of digits (49), we get a square (890262070369 = 943537²).

The spelling of 18168613681 in words is "eighteen billion, one hundred sixty-eight million, six hundred thirteen thousand, six hundred eighty-one".