2001691 has 2 divisors, whose sum is σ = 2001692. Its totient is φ = 2001690.

The previous prime is 2001677. The next prime is 2001697. The reversal of 2001691 is 1961002.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 2001691 - 2⁹ = 2001179 is a prime.

It is a plaindrome in base 11.

It is not a weakly prime, because it can be changed into another prime (2001697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1000845 + 1000846.

It is an arithmetic number, because the mean of its divisors is an integer number (1000846).

2^2001691 is an apocalyptic number.

2001691 is a deficient number, since it is larger than the sum of its proper divisors (1).

2001691 is an equidigital number, since it uses as much as digits as its factorization.

2001691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 2001691 is about 1414.8112948376. The cubic root of 2001691 is about 126.0276037616.

Adding to 2001691 its reverse (1961002), we get a palindrome (3962693).

It can be divided in two parts, 200 and 1691, that added together give a triangular number (1891 = T₆₁).

The spelling of 2001691 in words is "two million, one thousand, six hundred ninety-one".