6991217216281 has 3 divisors (see below), whose sum is σ = 6991219860373. Its totient is φ = 6991214572190.

The previous prime is 6991217216173. The next prime is 6991217216317. The reversal of 6991217216281 is 1826127121996.

The square root of 6991217216281 is 2644091.

It is a perfect power (a square), and thus also a powerful number.

6991217216281 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 6991217216281 - 2⁷ = 6991217216153 is a prime.

It is a super-2 number, since 2×6991217216281² (a number of 26 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6991217216881) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 1322046 + ... + 3966136.

Almost surely, 2^{6991217216281} is an apocalyptic number.

6991217216281 is the 2644091-st square number.

6991217216281 is the 1322046-th centered octagonal number.

It is an amenable number.

6991217216281 is a deficient number, since it is larger than the sum of its proper divisors (2644092).

6991217216281 is an frugal number, since it uses more digits than its factorization.

6991217216281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5288182 (or 2644091 counting only the distinct ones).

The product of its digits is 1306368, while the sum is 55.

The spelling of 6991217216281 in words is "six trillion, nine hundred ninety-one billion, two hundred seventeen million, two hundred sixteen thousand, two hundred eighty-one".