43681 has 9 divisors (see below), whose sum is σ = 50673. Its totient is φ = 37620.

The previous prime is 43669. The next prime is 43691. The reversal of 43681 is 18634.

43681 = T₂₀₈ + T₂₀₉.

The square root of 43681 is 209.

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

43681 is nontrivially palindromic in base 13.

It is not a de Polignac number, because 43681 - 2⁵ = 43649 is a prime.

It is a super-2 number, since 2×43681² = 3816059522, which contains 22 as substring.

43681 is a lucky number.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (43651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2290 + ... + 2308.

2⁴³⁶⁸¹ is an apocalyptic number.

43681 is the 209-th square number and also the 121-st octagonal number.

43681 is the 105-th centered octagonal number.

It is an amenable number.

43681 is a deficient number, since it is larger than the sum of its proper divisors (6992).

43681 is a wasteful number, since it uses less digits than its factorization.

With its predecessor (43680) it forms a Ruth-Aaron pair, since the sum of their distinct prime factors is the same (30).

43681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60 (or 30 counting only the distinct ones).

The product of its digits is 576, while the sum is 22.

The cubic root of 43681 is about 35.2179595852.

Multiplying 43681 by its product of digits (576), we get a square (25160256 = 5016²).

The spelling of 43681 in words is "forty-three thousand, six hundred eighty-one".