43681681 has 4 divisors (see below), whose sum is σ = 43705012. Its totient is φ = 43658352.

The previous prime is 43681661. The next prime is 43681691. The reversal of 43681681 is 18618634.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18618634 = 2 ⋅9309317.

It can be written as a sum of positive squares in 2 ways, for example, as 10504081 + 33177600 = 3241^2 + 5760^2 .

It is a cyclic number.

It is not a de Polignac number, because 43681681 - 2⁷ = 43681553 is a prime.

It is a super-2 number, since 2×43681681² = 3816178509971522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 43681681.

It is not an unprimeable number, because it can be changed into a prime (43681661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8586 + ... + 12691.

It is an arithmetic number, because the mean of its divisors is an integer number (10926253).

Almost surely, 2^43681681 is an apocalyptic number.

It is an amenable number.

43681681 is a deficient number, since it is larger than the sum of its proper divisors (23331).

43681681 is a wasteful number, since it uses less digits than its factorization.

43681681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23330.

The product of its digits is 27648, while the sum is 37.

The square root of 43681681 is about 6609.2118289551. The cubic root of 43681681 is about 352.1814260378.

The spelling of 43681681 in words is "forty-three million, six hundred eighty-one thousand, six hundred eighty-one".