210653981 has 2 divisors, whose sum is σ = 210653982. Its totient is φ = 210653980.

The previous prime is 210653977. The next prime is 210654029. The reversal of 210653981 is 189356012.

210653981 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., 113316025 + 97337956 = 10645^2 + 9866^2 .

It is a cyclic number.

It is not a de Polignac number, because 210653981 - 2² = 210653977 is a prime.

It is a super-2 number, since 2×210653981² = 88750199422296722, 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 (210653921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 105326990 + 105326991.

It is an arithmetic number, because the mean of its divisors is an integer number (105326991).

Almost surely, 2^210653981 is an apocalyptic number.

It is an amenable number.

210653981 is a deficient number, since it is larger than the sum of its proper divisors (1).

210653981 is an equidigital number, since it uses as much as digits as its factorization.

210653981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 35.

The square root of 210653981 is about 14513.9236941635. The cubic root of 210653981 is about 595.0085736589.

The spelling of 210653981 in words is "two hundred ten million, six hundred fifty-three thousand, nine hundred eighty-one".