43561681 has 2 divisors, whose sum is σ = 43561682. Its totient is φ = 43561680.

The previous prime is 43561643. The next prime is 43561703. The reversal of 43561681 is 18616534.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 43560000 + 1681 = 6600^2 + 41^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-43561681 is a prime.

It is a super-2 number, since 2×43561681² = 3795240103091522, which contains 22 as substring.

It is equal to p_2636539 and since 43561681 and 2636539 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (43561181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21780840 + 21780841.

It is an arithmetic number, because the mean of its divisors is an integer number (21780841).

Almost surely, 2^43561681 is an apocalyptic number.

It is an amenable number.

43561681 is a deficient number, since it is larger than the sum of its proper divisors (1).

43561681 is an equidigital number, since it uses as much as digits as its factorization.

43561681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17280, while the sum is 34.

The square root of 43561681 is about 6600.1273472563. The cubic root of 43561681 is about 351.8586322175.

It can be divided in two parts, 4356 and 1681, that multiplied together give a square (7322436 = 2706²).

The spelling of 43561681 in words is "forty-three million, five hundred sixty-one thousand, six hundred eighty-one".