6991643 has 4 divisors (see below), whose sum is σ = 7007400. Its totient is φ = 6975888.

The previous prime is 6991619. The next prime is 6991657. The reversal of 6991643 is 3461996.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 6991643 - 2¹⁰ = 6990619 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 6991597 and 6991606.

It is not an unprimeable number, because it can be changed into a prime (6991603) 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, 7193 + ... + 8106.

It is an arithmetic number, because the mean of its divisors is an integer number (1751850).

Almost surely, 2^6991643 is an apocalyptic number.

6991643 is a deficient number, since it is larger than the sum of its proper divisors (15757).

6991643 is a wasteful number, since it uses less digits than its factorization.

6991643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15756.

The product of its digits is 34992, while the sum is 38.

The square root of 6991643 is about 2644.1715148606. The cubic root of 6991643 is about 191.2169624109.

The spelling of 6991643 in words is "six million, nine hundred ninety-one thousand, six hundred forty-three".