209740221 has 24 divisors (see below), whose sum is σ = 324324000. Its totient is φ = 130216032.

The previous prime is 209740213. The next prime is 209740247. The reversal of 209740221 is 122047902.

It is not a de Polignac number, because 209740221 - 2³ = 209740213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209740211) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 306 + ... + 20483.

It is an arithmetic number, because the mean of its divisors is an integer number (13513500).

Almost surely, 2^209740221 is an apocalyptic number.

It is an amenable number.

209740221 is a deficient number, since it is larger than the sum of its proper divisors (114583779).

209740221 is a wasteful number, since it uses less digits than its factorization.

209740221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20873 (or 20870 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 209740221 is about 14482.4107454526. The cubic root of 209740221 is about 594.1469979355.

The spelling of 209740221 in words is "two hundred nine million, seven hundred forty thousand, two hundred twenty-one".