43681661 has 2 divisors, whose sum is σ = 43681662. Its totient is φ = 43681660.

The previous prime is 43681637. The next prime is 43681691. The reversal of 43681661 is 16618634.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43309561 + 372100 = 6581^2 + 610^2 .

It is a cyclic number.

It is not a de Polignac number, because 43681661 - 2⁶ = 43681597 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (43681691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21840830 + 21840831.

It is an arithmetic number, because the mean of its divisors is an integer number (21840831).

Almost surely, 2^43681661 is an apocalyptic number.

It is an amenable number.

43681661 is a deficient number, since it is larger than the sum of its proper divisors (1).

43681661 is an equidigital number, since it uses as much as digits as its factorization.

43681661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20736, while the sum is 35.

The square root of 43681661 is about 6609.2103159152. The cubic root of 43681661 is about 352.1813722881.

The spelling of 43681661 in words is "forty-three million, six hundred eighty-one thousand, six hundred sixty-one".