1971691 has 2 divisors, whose sum is σ = 1971692. Its totient is φ = 1971690.

The previous prime is 1971667. The next prime is 1971707. The reversal of 1971691 is 1961791.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1971691 - 2⁵ = 1971659 is a prime.

It is not a weakly prime, because it can be changed into another prime (1971601) 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 as a sum of consecutive naturals, namely, 985845 + 985846.

It is an arithmetic number, because the mean of its divisors is an integer number (985846).

2^1971691 is an apocalyptic number.

1971691 is a deficient number, since it is larger than the sum of its proper divisors (1).

1971691 is an equidigital number, since it uses as much as digits as its factorization.

1971691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3402, while the sum is 34.

The square root of 1971691 is about 1404.1691493549. The cubic root of 1971691 is about 125.3948262515.

It can be divided in two parts, 1971 and 691, that added together give a palindrome (2662).

The spelling of 1971691 in words is "one million, nine hundred seventy-one thousand, six hundred ninety-one".