1808188506721 has 9 divisors (see below), whose sum is σ = 1811379694233. Its totient is φ = 1805002938480.

The previous prime is 1808188506673. The next prime is 1808188506737. The reversal of 1808188506721 is 1276058818081.

The square root of 1808188506721 is 1344689.

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 276138689121 + 1532049817600 = 525489^2 + 1237760^2 .

It is not a de Polignac number, because 1808188506721 - 2¹⁵ = 1808188473953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1808188566721) 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, 1265351635 + ... + 1265353063.

Almost surely, 2^{1808188506721} is an apocalyptic number.

1808188506721 is the 1344689-th square number.

1808188506721 is the 672345-th centered octagonal number.

It is an amenable number.

1808188506721 is a deficient number, since it is larger than the sum of its proper divisors (3191187512).

1808188506721 is an frugal number, since it uses more digits than its factorization.

1808188506721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4740 (or 2370 counting only the distinct ones).

The product of its (nonzero) digits is 1720320, while the sum is 55.

The spelling of 1808188506721 in words is "one trillion, eight hundred eight billion, one hundred eighty-eight million, five hundred six thousand, seven hundred twenty-one".