43651981 has 2 divisors, whose sum is σ = 43651982. Its totient is φ = 43651980.

The previous prime is 43651967. The next prime is 43651997. The reversal of 43651981 is 18915634.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 32959081 + 10692900 = 5741^2 + 3270^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-43651981 is a prime.

It is a super-2 number, since 2×43651981² = 3810990890448722, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 43651981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (43651961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21825990 + 21825991.

It is an arithmetic number, because the mean of its divisors is an integer number (21825991).

Almost surely, 2^43651981 is an apocalyptic number.

It is an amenable number.

43651981 is a deficient number, since it is larger than the sum of its proper divisors (1).

43651981 is an equidigital number, since it uses as much as digits as its factorization.

43651981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 37.

The square root of 43651981 is about 6606.9645829231. The cubic root of 43651981 is about 352.1015896730.

The spelling of 43651981 in words is "forty-three million, six hundred fifty-one thousand, nine hundred eighty-one".