206639499221 has 2 divisors, whose sum is σ = 206639499222. Its totient is φ = 206639499220.

The previous prime is 206639499197. The next prime is 206639499251. The reversal of 206639499221 is 122994936602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 206383947025 + 255552196 = 454295^2 + 15986^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-206639499221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206639499251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103319749610 + 103319749611.

It is an arithmetic number, because the mean of its divisors is an integer number (103319749611).

Almost surely, 2^206639499221 is an apocalyptic number.

It is an amenable number.

206639499221 is a deficient number, since it is larger than the sum of its proper divisors (1).

206639499221 is an equidigital number, since it uses as much as digits as its factorization.

206639499221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2519424, while the sum is 53.

The spelling of 206639499221 in words is "two hundred six billion, six hundred thirty-nine million, four hundred ninety-nine thousand, two hundred twenty-one".