206021681 has 2 divisors, whose sum is σ = 206021682. Its totient is φ = 206021680.

The previous prime is 206021677. The next prime is 206021749. The reversal of 206021681 is 186120602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 202350625 + 3671056 = 14225^2 + 1916^2 .

It is a cyclic number.

It is not a de Polignac number, because 206021681 - 2² = 206021677 is a prime.

It is a super-2 number, since 2×206021681² = 84889866084131522, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 206021681.

It is not a weakly prime, because it can be changed into another prime (206021671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103010840 + 103010841.

It is an arithmetic number, because the mean of its divisors is an integer number (103010841).

Almost surely, 2^206021681 is an apocalyptic number.

It is an amenable number.

206021681 is a deficient number, since it is larger than the sum of its proper divisors (1).

206021681 is an equidigital number, since it uses as much as digits as its factorization.

206021681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 206021681 is about 14353.4553679593. The cubic root of 206021681 is about 590.6147771660.

The spelling of 206021681 in words is "two hundred six million, twenty-one thousand, six hundred eighty-one".