209206526881 has 27 divisors (see below), whose sum is σ = 235670134833. Its totient is φ = 185572676520.

The previous prime is 209206526803. The next prime is 209206526899. The reversal of 209206526881 is 188625602902.

It is a happy number.

The square root of 209206526881 is 457391.

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

It is not a de Polignac number, because 209206526881 - 2¹¹ = 209206524833 is a prime.

It is a super-2 number, since 2×209206526881² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209206526381) 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, 216345460 + ... + 216346426.

Almost surely, 2^209206526881 is an apocalyptic number.

209206526881 is the 457391-st square number.

209206526881 is the 228696-th centered octagonal number.

It is an amenable number.

209206526881 is a deficient number, since it is larger than the sum of its proper divisors (26463607952).

209206526881 is an frugal number, since it uses more digits than its factorization.

209206526881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2042 (or 1021 counting only the distinct ones).

The product of its (nonzero) digits is 829440, while the sum is 49.

Multiplying 209206526881 by its sum of digits (49), we get a square (10251119817169 = 3201737²).

The spelling of 209206526881 in words is "two hundred nine billion, two hundred six million, five hundred twenty-six thousand, eight hundred eighty-one".