43661981 has 32 divisors (see below), whose sum is σ = 54190080. Its totient is φ = 34689600.

The previous prime is 43661963. The next prime is 43662011. The reversal of 43661981 is 18916634.

It is not a de Polignac number, because 43661981 - 2²² = 39467677 is a prime.

It is a super-2 number, since 2×43661981² = 3812737169688722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (43661921) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 148871 + ... + 149163.

It is an arithmetic number, because the mean of its divisors is an integer number (1693440).

Almost surely, 2^43661981 is an apocalyptic number.

It is an amenable number.

43661981 is a deficient number, since it is larger than the sum of its proper divisors (10528099).

43661981 is a wasteful number, since it uses less digits than its factorization.

43661981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 377.

The product of its digits is 31104, while the sum is 38.

The square root of 43661981 is about 6607.7213167627. The cubic root of 43661981 is about 352.1284746466.

The spelling of 43661981 in words is "forty-three million, six hundred sixty-one thousand, nine hundred eighty-one".