6991638836 has 72 divisors (see below), whose sum is σ = 15494238144. Its totient is φ = 2701520640.

The previous prime is 6991638821. The next prime is 6991638839. The reversal of 6991638836 is 6388361996.

It is a super-2 number, since 2×6991638836² = 97766027226126869792, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6991638839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 186296 + ... + 220656.

It is an arithmetic number, because the mean of its divisors is an integer number (215197752).

Almost surely, 2^6991638836 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6991638836, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (7747119072).

6991638836 is an abundant number, since it is smaller than the sum of its proper divisors (8502599308).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6991638836 is a wasteful number, since it uses less digits than its factorization.

6991638836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34441 (or 34426 counting only the distinct ones).

The product of its digits is 10077696, while the sum is 59.

The square root of 6991638836 is about 83616.0202114403. The cubic root of 6991638836 is about 1912.1692444999.

The spelling of 6991638836 in words is "six billion, nine hundred ninety-one million, six hundred thirty-eight thousand, eight hundred thirty-six".