691861187 has 4 divisors (see below), whose sum is σ = 710560176. Its totient is φ = 673162200.

The previous prime is 691861151. The next prime is 691861201. The reversal of 691861187 is 781168196.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691861187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (691861987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9349439 + ... + 9349512.

It is an arithmetic number, because the mean of its divisors is an integer number (177640044).

Almost surely, 2^691861187 is an apocalyptic number.

691861187 is a deficient number, since it is larger than the sum of its proper divisors (18698989).

691861187 is a wasteful number, since it uses less digits than its factorization.

691861187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18698988.

The product of its digits is 145152, while the sum is 47.

The square root of 691861187 is about 26303.2543043632. The cubic root of 691861187 is about 884.4493950277.

The spelling of 691861187 in words is "six hundred ninety-one million, eight hundred sixty-one thousand, one hundred eighty-seven".