691187009 has 4 divisors (see below), whose sum is σ = 692837040. Its totient is φ = 689536980.

The previous prime is 691186967. The next prime is 691187023. The reversal of 691187009 is 900781196.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691187009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (691187039) 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 in 3 ways as a sum of consecutive naturals, for example, 824387 + ... + 825224.

It is an arithmetic number, because the mean of its divisors is an integer number (173209260).

Almost surely, 2^691187009 is an apocalyptic number.

It is an amenable number.

691187009 is a deficient number, since it is larger than the sum of its proper divisors (1650031).

691187009 is a wasteful number, since it uses less digits than its factorization.

691187009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1650030.

The product of its (nonzero) digits is 27216, while the sum is 41.

The square root of 691187009 is about 26290.4356943737. The cubic root of 691187009 is about 884.1620203736.

The spelling of 691187009 in words is "six hundred ninety-one million, one hundred eighty-seven thousand, nine".