6906221981 has 2 divisors, whose sum is σ = 6906221982. Its totient is φ = 6906221980.

The previous prime is 6906221977. The next prime is 6906222019. The reversal of 6906221981 is 1891226096.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5068728025 + 1837493956 = 71195^2 + 42866^2 .

It is a cyclic number.

It is not a de Polignac number, because 6906221981 - 2² = 6906221977 is a prime.

It is a super-2 number, since 2×6906221981² = 95391804101695128722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6906221921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3453110990 + 3453110991.

It is an arithmetic number, because the mean of its divisors is an integer number (3453110991).

Almost surely, 2^6906221981 is an apocalyptic number.

It is an amenable number.

6906221981 is a deficient number, since it is larger than the sum of its proper divisors (1).

6906221981 is an equidigital number, since it uses as much as digits as its factorization.

6906221981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 93312, while the sum is 44.

The square root of 6906221981 is about 83103.6821145730. The cubic root of 6906221981 is about 1904.3503254183.

The spelling of 6906221981 in words is "six billion, nine hundred six million, two hundred twenty-one thousand, nine hundred eighty-one".