690983981 has 2 divisors, whose sum is σ = 690983982. Its totient is φ = 690983980.

The previous prime is 690983959. The next prime is 690984011. The reversal of 690983981 is 189389096.

690983981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 637562500 + 53421481 = 25250^2 + 7309^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-690983981 is a prime.

It is a super-2 number, since 2×690983981² = 954917723997216722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen 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 (690983911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345491990 + 345491991.

It is an arithmetic number, because the mean of its divisors is an integer number (345491991).

Almost surely, 2^690983981 is an apocalyptic number.

It is an amenable number.

690983981 is a deficient number, since it is larger than the sum of its proper divisors (1).

690983981 is an equidigital number, since it uses as much as digits as its factorization.

690983981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 839808, while the sum is 53.

The square root of 690983981 is about 26286.5741586841. The cubic root of 690983981 is about 884.0754411876.

The spelling of 690983981 in words is "six hundred ninety million, nine hundred eighty-three thousand, nine hundred eighty-one".