2164640343781 has 4 divisors (see below), whose sum is σ = 2183796453132. Its totient is φ = 2145484234432.

The previous prime is 2164640343763. The next prime is 2164640343829. The reversal of 2164640343781 is 1873430464612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1189811916225 + 974828427556 = 1090785^2 + 987334^2 .

It is a cyclic number.

It is not a de Polignac number, because 2164640343781 - 2⁹ = 2164640343269 is a prime.

It is a super-2 number, since 2×2164640343781² (a number of 25 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2164640343721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9578054506 + ... + 9578054731.

It is an arithmetic number, because the mean of its divisors is an integer number (545949113283).

Almost surely, 2^{2164640343781} is an apocalyptic number.

It is an amenable number.

2164640343781 is a deficient number, since it is larger than the sum of its proper divisors (19156109351).

2164640343781 is a wasteful number, since it uses less digits than its factorization.

2164640343781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19156109350.

The product of its (nonzero) digits is 2322432, while the sum is 49.

The spelling of 2164640343781 in words is "two trillion, one hundred sixty-four billion, six hundred forty million, three hundred forty-three thousand, seven hundred eighty-one".