40643665921 has 16 divisors (see below), whose sum is σ = 41350843600. Its totient is φ = 39943507968.

The previous prime is 40643665901. The next prime is 40643665927. The reversal of 40643665921 is 12956634604.

It can be written as a sum of positive squares in 8 ways, for example, as 4290905025 + 36352760896 = 65505^2 + 190664^2 .

It is a cyclic number.

It is not a de Polignac number, because 40643665921 - 2⁹ = 40643665409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (40643665927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11515285 + ... + 11518813.

It is an arithmetic number, because the mean of its divisors is an integer number (2584427725).

Almost surely, 2^40643665921 is an apocalyptic number.

It is an amenable number.

40643665921 is a deficient number, since it is larger than the sum of its proper divisors (707177679).

40643665921 is a wasteful number, since it uses less digits than its factorization.

40643665921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4468.

The product of its (nonzero) digits is 933120, while the sum is 46.

The spelling of 40643665921 in words is "forty billion, six hundred forty-three million, six hundred sixty-five thousand, nine hundred twenty-one".