6991207649 has 2 divisors, whose sum is σ = 6991207650. Its totient is φ = 6991207648.

The previous prime is 6991207631. The next prime is 6991207651. The reversal of 6991207649 is 9467021996.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5906691025 + 1084516624 = 76855^2 + 32932^2 .

It is a cyclic number.

It is not a de Polignac number, because 6991207649 - 2²⁴ = 6974430433 is a prime.

It is a super-2 number, since 2×6991207649² = 97753968782872214402, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 6991207651, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 6991207649.

It is not a weakly prime, because it can be changed into another prime (6991207679) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3495603824 + 3495603825.

It is an arithmetic number, because the mean of its divisors is an integer number (3495603825).

Almost surely, 2^6991207649 is an apocalyptic number.

It is an amenable number.

6991207649 is a deficient number, since it is larger than the sum of its proper divisors (1).

6991207649 is an equidigital number, since it uses as much as digits as its factorization.

6991207649 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1469664, while the sum is 53.

The square root of 6991207649 is about 83613.4417961610. The cubic root of 6991207649 is about 1912.1299347143.

The spelling of 6991207649 in words is "six billion, nine hundred ninety-one million, two hundred seven thousand, six hundred forty-nine".