209678820649 has 27 divisors (see below), whose sum is σ = 224893414557. Its totient is φ = 195475003416.

The previous prime is 209678820647. The next prime is 209678820653. The reversal of 209678820649 is 946028876902.

The square root of 209678820649 is 457907.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 209678820649 - 2¹ = 209678820647 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209678820647) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 452869792 + ... + 452870254.

Almost surely, 2^209678820649 is an apocalyptic number.

209678820649 is the 457907-th square number.

209678820649 is the 228954-th centered octagonal number.

It is an amenable number.

209678820649 is a deficient number, since it is larger than the sum of its proper divisors (15214593908).

209678820649 is an frugal number, since it uses more digits than its factorization.

209678820649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1058 (or 529 counting only the distinct ones).

The product of its (nonzero) digits is 20901888, while the sum is 61.

The spelling of 209678820649 in words is "two hundred nine billion, six hundred seventy-eight million, eight hundred twenty thousand, six hundred forty-nine".