2001781667 has 4 divisors (see below), whose sum is σ = 2008218576. Its totient is φ = 1995344760.

The previous prime is 2001781601. The next prime is 2001781679. The reversal of 2001781667 is 7661871002.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7661871002 = 2 ⋅3830935501.

It is a cyclic number.

It is not a de Polignac number, because 2001781667 - 2¹⁶ = 2001716131 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 2001781667.

It is not an unprimeable number, because it can be changed into a prime (2001781697) 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, 3217988 + ... + 3218609.

It is an arithmetic number, because the mean of its divisors is an integer number (502054644).

Almost surely, 2^2001781667 is an apocalyptic number.

2001781667 is a deficient number, since it is larger than the sum of its proper divisors (6436909).

2001781667 is an equidigital number, since it uses as much as digits as its factorization.

2001781667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6436908.

The product of its (nonzero) digits is 28224, while the sum is 38.

The square root of 2001781667 is about 44741.2747583258. The cubic root of 2001781667 is about 1260.2950654812.

The spelling of 2001781667 in words is "two billion, one million, seven hundred eighty-one thousand, six hundred sixty-seven".