691087 has 4 divisors (see below), whose sum is σ = 727480. Its totient is φ = 654696.

The previous prime is 691079. The next prime is 691109. The reversal of 691087 is 780196.

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 691087 - 2³ = 691079 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 (691037) 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, 18168 + ... + 18205.

It is an arithmetic number, because the mean of its divisors is an integer number (181870).

2⁶⁹¹⁰⁸⁷ is an apocalyptic number.

691087 is a deficient number, since it is larger than the sum of its proper divisors (36393).

691087 is a wasteful number, since it uses less digits than its factorization.

691087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36392.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 691087 is about 831.3164259174. The cubic root of 691087 is about 88.4119374691.

It can be divided in two parts, 69 and 1087, that added together give a square (1156 = 34²).

The spelling of 691087 in words is "six hundred ninety-one thousand, eighty-seven".