43105509721 has 2 divisors, whose sum is σ = 43105509722. Its totient is φ = 43105509720.

The previous prime is 43105509719. The next prime is 43105509751. The reversal of 43105509721 is 12790550134.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 37839975625 + 5265534096 = 194525^2 + 72564^2 .

It is a cyclic number.

It is not a de Polignac number, because 43105509721 - 2¹ = 43105509719 is a prime.

Together with 43105509719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (43105509701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21552754860 + 21552754861.

It is an arithmetic number, because the mean of its divisors is an integer number (21552754861).

Almost surely, 2^43105509721 is an apocalyptic number.

It is an amenable number.

43105509721 is a deficient number, since it is larger than the sum of its proper divisors (1).

43105509721 is an equidigital number, since it uses as much as digits as its factorization.

43105509721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 37800, while the sum is 37.

It can be divided in two parts, 43105 and 509721, that added together give a triangular number (552826 = T₁₀₅₁).

The spelling of 43105509721 in words is "forty-three billion, one hundred five million, five hundred nine thousand, seven hundred twenty-one".