81000018000001 has 9 divisors (see below), whose sum is σ = 82350213645609. Its totient is φ = 79671608852400.

The previous prime is 81000017999947. The next prime is 81000018000029. The reversal of 81000018000001 is 10000081000018.

The square root of 81000018000001 is 9000001.

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

It can be written as a sum of positive squares in 4 ways, for example, as 70842539073601 + 10157478926400 = 8416801^2 + 3187080^2 .

It is not a de Polignac number, because 81000018000001 - 2²⁹ = 80999481129089 is a prime.

It is a super-2 number, since 2×81000018000001² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81000018000701) 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, 548926291 + ... + 549073831.

It is an arithmetic number, because the mean of its divisors is an integer number (9150023738401).

Almost surely, 2^{81000018000001} is an apocalyptic number.

81000018000001 is the 9000001-st square number.

81000018000001 is the 4500001-st centered octagonal number.

It is an amenable number.

81000018000001 is a deficient number, since it is larger than the sum of its proper divisors (1350195645608).

81000018000001 is an frugal number, since it uses more digits than its factorization.

81000018000001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 295204 (or 147602 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 19.

Adding to 81000018000001 its reverse (10000081000018), we get a palindrome (91000099000019).

The spelling of 81000018000001 in words is "eighty-one trillion, eighteen million, one", and thus it is an aban number and an uban number.