43666656221 has 4 divisors (see below), whose sum is σ = 43667110944. Its totient is φ = 43666201500.

The previous prime is 43666656151. The next prime is 43666656223. The reversal of 43666656221 is 12265666634.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 43666656221 - 2¹⁸ = 43666394077 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (43666656223) 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, 20705 + ... + 296246.

It is an arithmetic number, because the mean of its divisors is an integer number (10916777736).

Almost surely, 2^43666656221 is an apocalyptic number.

It is an amenable number.

43666656221 is a deficient number, since it is larger than the sum of its proper divisors (454723).

43666656221 is a wasteful number, since it uses less digits than its factorization.

43666656221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 454722.

The product of its digits is 1866240, while the sum is 47.

The spelling of 43666656221 in words is "forty-three billion, six hundred sixty-six million, six hundred fifty-six thousand, two hundred twenty-one".