1971591 has 4 divisors (see below), whose sum is σ = 2628792. Its totient is φ = 1314392.

The previous prime is 1971589. The next prime is 1971601. The reversal of 1971591 is 1951791.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 1971591 - 2¹ = 1971589 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1971521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 328596 + ... + 328601.

It is an arithmetic number, because the mean of its divisors is an integer number (657198).

2^1971591 is an apocalyptic number.

1971591 is a deficient number, since it is larger than the sum of its proper divisors (657201).

1971591 is an equidigital number, since it uses as much as digits as its factorization.

1971591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 657200.

The product of its digits is 2835, while the sum is 33.

The square root of 1971591 is about 1404.1335406577. The cubic root of 1971591 is about 125.3927062955.

The spelling of 1971591 in words is "one million, nine hundred seventy-one thousand, five hundred ninety-one".