197991526591 has 4 divisors (see below), whose sum is σ = 201237289384. Its totient is φ = 194745763800.

The previous prime is 197991526571. The next prime is 197991526619. The reversal of 197991526591 is 195625199791.

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 197991526591 - 2⁷ = 197991526463 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (197991526571) 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, 1622881305 + ... + 1622881426.

It is an arithmetic number, because the mean of its divisors is an integer number (50309322346).

Almost surely, 2^197991526591 is an apocalyptic number.

197991526591 is a deficient number, since it is larger than the sum of its proper divisors (3245762793).

197991526591 is an equidigital number, since it uses as much as digits as its factorization.

197991526591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3245762792.

The product of its digits is 13778100, while the sum is 64.

The spelling of 197991526591 in words is "one hundred ninety-seven billion, nine hundred ninety-one million, five hundred twenty-six thousand, five hundred ninety-one".