6991309 has 4 divisors (see below), whose sum is σ = 7529116. Its totient is φ = 6453504.

The previous prime is 6991289. The next prime is 6991319. The reversal of 6991309 is 9031996.

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

It can be written as a sum of positive squares in 2 ways, for example, as 2673225 + 4318084 = 1635^2 + 2078^2 .

It is a cyclic number.

It is not a de Polignac number, because 6991309 - 2⁵ = 6991277 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 (6991319) 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, 268884 + ... + 268909.

It is an arithmetic number, because the mean of its divisors is an integer number (1882279).

Almost surely, 2^6991309 is an apocalyptic number.

It is an amenable number.

6991309 is a deficient number, since it is larger than the sum of its proper divisors (537807).

6991309 is a wasteful number, since it uses less digits than its factorization.

6991309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 537806.

The product of its (nonzero) digits is 13122, while the sum is 37.

The square root of 6991309 is about 2644.1083563273. The cubic root of 6991309 is about 191.2139174670.

It can be divided in two parts, 69 and 91309, that added together give a triangular number (91378 = T₄₂₇).

The spelling of 6991309 in words is "six million, nine hundred ninety-one thousand, three hundred nine".