181521729 has 21 divisors (see below), whose sum is σ = 272704593. Its totient is φ = 120771972.

The previous prime is 181521721. The next prime is 181521737. The reversal of 181521729 is 927125181.

It is a happy number.

The square root of 181521729 is 13473.

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 (181521721) and next prime (181521737).

It is not a de Polignac number, because 181521729 - 2³ = 181521721 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 181521693 and 181521702.

It is not an unprimeable number, because it can be changed into a prime (181521721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 363522 + ... + 364020.

It is an arithmetic number, because the mean of its divisors is an integer number (12985933).

Almost surely, 2^181521729 is an apocalyptic number.

181521729 is the 13473-rd square number.

181521729 is the 6737-th centered octagonal number.

It is an amenable number.

181521729 is a deficient number, since it is larger than the sum of its proper divisors (91182864).

181521729 is an frugal number, since it uses more digits than its factorization.

181521729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1016 (or 502 counting only the distinct ones).

The product of its digits is 10080, while the sum is 36.

The cubic root of 181521729 is about 566.2082676143.

Multiplying 181521729 by its sum of digits (36), we get a square (6534782244 = 80838²).

It can be divided in two parts, 18152 and 1729, that added together give a square (19881 = 141²).

The spelling of 181521729 in words is "one hundred eighty-one million, five hundred twenty-one thousand, seven hundred twenty-nine".