6391681 has 4 divisors (see below), whose sum is σ = 6424000. Its totient is φ = 6359364.

The previous prime is 6391669. The next prime is 6391699. The reversal of 6391681 is 1861936.

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 not a de Polignac number, because 6391681 - 2²¹ = 4294529 is a prime.

It is a super-2 number, since 2×6391681² = 81707172011522, which contains 22 as substring.

It is a Duffinian number.

6391681 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (6391601) 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, 15861 + ... + 16258.

It is an arithmetic number, because the mean of its divisors is an integer number (1606000).

Almost surely, 2^6391681 is an apocalyptic number.

It is an amenable number.

6391681 is a deficient number, since it is larger than the sum of its proper divisors (32319).

6391681 is a wasteful number, since it uses less digits than its factorization.

6391681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32318.

The product of its digits is 7776, while the sum is 34.

The square root of 6391681 is about 2528.1774067498. The cubic root of 6391681 is about 185.5830739277.

The spelling of 6391681 in words is "six million, three hundred ninety-one thousand, six hundred eighty-one".