691661273 has 8 divisors (see below), whose sum is σ = 698235720. Its totient is φ = 685117440.

The previous prime is 691661251. The next prime is 691661293. The reversal of 691661273 is 372166196.

It can be written as a sum of positive squares in 4 ways, for example, as 39778249 + 651883024 = 6307^2 + 25532^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691661273 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 691661273.

It is not an unprimeable number, because it can be changed into a prime (691661213) 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 7 ways as a sum of consecutive naturals, for example, 39083 + ... + 53951.

It is an arithmetic number, because the mean of its divisors is an integer number (87279465).

Almost surely, 2^691661273 is an apocalyptic number.

It is an amenable number.

691661273 is a deficient number, since it is larger than the sum of its proper divisors (6574447).

691661273 is a wasteful number, since it uses less digits than its factorization.

691661273 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15307.

The product of its digits is 81648, while the sum is 41.

The square root of 691661273 is about 26299.4538536449. The cubic root of 691661273 is about 884.3641993012.

The spelling of 691661273 in words is "six hundred ninety-one million, six hundred sixty-one thousand, two hundred seventy-three".