687191321 has 4 divisors (see below), whose sum is σ = 696870144. Its totient is φ = 677512500.

The previous prime is 687191317. The next prime is 687191333. The reversal of 687191321 is 123191786.

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, and also an emirpimes, since its reverse is a distinct semiprime: 123191786 = 2 ⋅61595893.

It is a cyclic number.

It is not a de Polignac number, because 687191321 - 2² = 687191317 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (687191311) 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, 4839305 + ... + 4839446.

It is an arithmetic number, because the mean of its divisors is an integer number (174217536).

Almost surely, 2^687191321 is an apocalyptic number.

It is an amenable number.

687191321 is a deficient number, since it is larger than the sum of its proper divisors (9678823).

687191321 is an equidigital number, since it uses as much as digits as its factorization.

687191321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9678822.

The product of its digits is 18144, while the sum is 38.

The square root of 687191321 is about 26214.3342658172. The cubic root of 687191321 is about 882.4549738281.

The spelling of 687191321 in words is "six hundred eighty-seven million, one hundred ninety-one thousand, three hundred twenty-one".