209106986981 has 2 divisors, whose sum is σ = 209106986982. Its totient is φ = 209106986980.

The previous prime is 209106986971. The next prime is 209106986999. The reversal of 209106986981 is 189689601902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 208726541956 + 380445025 = 456866^2 + 19505^2 .

It is a cyclic number.

It is not a de Polignac number, because 209106986981 - 2¹⁸ = 209106724837 is a prime.

It is a super-2 number, since 2×209106986981² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 209106986981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (209106986971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104553493490 + 104553493491.

It is an arithmetic number, because the mean of its divisors is an integer number (104553493491).

Almost surely, 2^209106986981 is an apocalyptic number.

It is an amenable number.

209106986981 is a deficient number, since it is larger than the sum of its proper divisors (1).

209106986981 is an equidigital number, since it uses as much as digits as its factorization.

209106986981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3359232, while the sum is 59.

The spelling of 209106986981 in words is "two hundred nine billion, one hundred six million, nine hundred eighty-six thousand, nine hundred eighty-one".