6921999791 has 4 divisors (see below), whose sum is σ = 7910856912. Its totient is φ = 5933142672.

The previous prime is 6921999787. The next prime is 6921999797. The reversal of 6921999791 is 1979991296.

It is a happy number.

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 6921999791 - 2² = 6921999787 is a prime.

It is a super-2 number, since 2×6921999791² = 95828162213208087362, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6921999797) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 494428550 + ... + 494428563.

It is an arithmetic number, because the mean of its divisors is an integer number (1977714228).

Almost surely, 2^6921999791 is an apocalyptic number.

6921999791 is a deficient number, since it is larger than the sum of its proper divisors (988857121).

6921999791 is an equidigital number, since it uses as much as digits as its factorization.

6921999791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 988857120.

The product of its digits is 4960116, while the sum is 62.

The square root of 6921999791 is about 83198.5564237746. The cubic root of 6921999791 is about 1905.7994353901.

The spelling of 6921999791 in words is "six billion, nine hundred twenty-one million, nine hundred ninety-nine thousand, seven hundred ninety-one".