8181000000 has 490 divisors, whose sum is σ = 30613553454. Its totient is φ = 2160000000.

The previous prime is 8180999839. The next prime is 8181000011. The reversal of 8181000000 is 1818.

It is a happy number.

It can be written as a sum of positive squares in 7 ways, for example, as 7640158464 + 540841536 = 87408^2 + 23256^2 .

It is a super-2 number, since 2×8181000000² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 69 ways as a sum of consecutive naturals, for example, 80999950 + ... + 81000050.

Almost surely, 2^8181000000 is an apocalyptic number.

8181000000 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 8181000000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (15306776727).

8181000000 is an abundant number, since it is smaller than the sum of its proper divisors (22432553454).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

8181000000 is an frugal number, since it uses more digits than its factorization.

8181000000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155 (or 111 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

The square root of 8181000000 is about 90448.8805900880. The cubic root of 8181000000 is about 2014.9709884643.

Adding to 8181000000 its reverse (1818), we get a palindrome (8181001818).

It can be divided in two parts, 81 and 81000000, that multiplied together give a square (6561000000 = 81000²).

The spelling of 8181000000 in words is "eight billion, one hundred eighty-one million", and thus it is an aban number.