6781991 has 8 divisors (see below), whose sum is σ = 6998400. Its totient is φ = 6569080.

The previous prime is 6781967. The next prime is 6782021. The reversal of 6781991 is 1991876.

It is a happy number.

6781991 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 6781991 - 2¹⁴ = 6765607 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6781961) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3380 + ... + 4998.

It is an arithmetic number, because the mean of its divisors is an integer number (874800).

Almost surely, 2^6781991 is an apocalyptic number.

6781991 is a deficient number, since it is larger than the sum of its proper divisors (216409).

6781991 is a wasteful number, since it uses less digits than its factorization.

6781991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1749.

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

The square root of 6781991 is about 2604.2256046664. The cubic root of 6781991 is about 189.2862510080.

The spelling of 6781991 in words is "six million, seven hundred eighty-one thousand, nine hundred ninety-one".