6687921 has 4 divisors (see below), whose sum is σ = 8917232. Its totient is φ = 4458612.

The previous prime is 6687881. The next prime is 6687931. The reversal of 6687921 is 1297866.

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 de Polignac number, because none of the positive numbers 2^k-6687921 is a prime.

It is a D-number.

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 6687921.

It is not an unprimeable number, because it can be changed into a prime (6687931) 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, 1114651 + ... + 1114656.

It is an arithmetic number, because the mean of its divisors is an integer number (2229308).

Almost surely, 2^6687921 is an apocalyptic number.

It is an amenable number.

6687921 is a deficient number, since it is larger than the sum of its proper divisors (2229311).

6687921 is a wasteful number, since it uses less digits than its factorization.

6687921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2229310.

The product of its digits is 36288, while the sum is 39.

The square root of 6687921 is about 2586.1015061285. The cubic root of 6687921 is about 188.4070045313.

The spelling of 6687921 in words is "six million, six hundred eighty-seven thousand, nine hundred twenty-one".