3821681665 has 4 divisors (see below), whose sum is σ = 4586018004. Its totient is φ = 3057345328.

The previous prime is 3821681663. The next prime is 3821681671. The reversal of 3821681665 is 5661861283.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5661861283 = 13 ⋅435527791.

It can be written as a sum of positive squares in 2 ways, for example, as 1527559056 + 2294122609 = 39084^2 + 47897^2 .

It is a cyclic number.

It is not a de Polignac number, because 3821681665 - 2¹ = 3821681663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3821681663) 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, 382168162 + ... + 382168171.

It is an arithmetic number, because the mean of its divisors is an integer number (1146504501).

Almost surely, 2^3821681665 is an apocalyptic number.

It is an amenable number.

3821681665 is a deficient number, since it is larger than the sum of its proper divisors (764336339).

3821681665 is an equidigital number, since it uses as much as digits as its factorization.

3821681665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 764336338.

The product of its digits is 414720, while the sum is 46.

The square root of 3821681665 is about 61819.7514148998. The cubic root of 3821681665 is about 1563.4530219293.

The spelling of 3821681665 in words is "three billion, eight hundred twenty-one million, six hundred eighty-one thousand, six hundred sixty-five".