6991120021 has 2 divisors, whose sum is σ = 6991120022. Its totient is φ = 6991120020.

The previous prime is 6991120013. The next prime is 6991120049. The reversal of 6991120021 is 1200211996.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6644043121 + 347076900 = 81511^2 + 18630^2 .

It is a cyclic number.

It is not a de Polignac number, because 6991120021 - 2³ = 6991120013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6991120051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3495560010 + 3495560011.

It is an arithmetic number, because the mean of its divisors is an integer number (3495560011).

Almost surely, 2^6991120021 is an apocalyptic number.

It is an amenable number.

6991120021 is a deficient number, since it is larger than the sum of its proper divisors (1).

6991120021 is an equidigital number, since it uses as much as digits as its factorization.

6991120021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 6991120021 is about 83612.9177878634. The cubic root of 6991120021 is about 1912.1219457835.

The spelling of 6991120021 in words is "six billion, nine hundred ninety-one million, one hundred twenty thousand, twenty-one".