209618739661 has 4 divisors (see below), whose sum is σ = 209660946912. Its totient is φ = 209576532412.

The previous prime is 209618739653. The next prime is 209618739703. The reversal of 209618739661 is 166937816902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 209618739661 - 2³ = 209618739653 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 209618739596 and 209618739605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209618739461) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21096175 + ... + 21106108.

It is an arithmetic number, because the mean of its divisors is an integer number (52415236728).

Almost surely, 2^209618739661 is an apocalyptic number.

It is an amenable number.

209618739661 is a deficient number, since it is larger than the sum of its proper divisors (42207251).

209618739661 is an equidigital number, since it uses as much as digits as its factorization.

209618739661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42207250.

The product of its (nonzero) digits is 5878656, while the sum is 58.

The spelling of 209618739661 in words is "two hundred nine billion, six hundred eighteen million, seven hundred thirty-nine thousand, six hundred sixty-one".