180821809 has 27 divisors (see below), whose sum is σ = 225439617. Its totient is φ = 144582144.

The previous prime is 180821783. The next prime is 180821813. The reversal of 180821809 is 908128081.

The square root of 180821809 is 13447.

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 22061809 + 158760000 = 4697^2 + 12600^2 .

It is not a de Polignac number, because 180821809 - 2¹¹ = 180819761 is a prime.

It is a super-2 number, since 2×180821809² = 65393053220064962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (180821819) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1600137 + ... + 1600249.

Almost surely, 2^180821809 is an apocalyptic number.

180821809 is the 13447-th square number.

180821809 is the 6724-th centered octagonal number.

It is an amenable number.

180821809 is a deficient number, since it is larger than the sum of its proper divisors (44617808).

180821809 is an equidigital number, since it uses as much as digits as its factorization.

180821809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 274 (or 137 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 37.

The cubic root of 180821809 is about 565.4795927888.

Multiplying 180821809 by its product of nonzero digits (9216), we get a square (1666453791744 = 1290912²).

It can be divided in two parts, 18082 and 1809, that added together give a palindrome (19891).

The spelling of 180821809 in words is "one hundred eighty million, eight hundred twenty-one thousand, eight hundred nine".