209340021 has 32 divisors (see below), whose sum is σ = 315518976. Its totient is φ = 122360000.

The previous prime is 209339971. The next prime is 209340037. The reversal of 209340021 is 120043902.

It is a cyclic number.

It is not a de Polignac number, because 209340021 - 2¹⁵ = 209307253 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 209340021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209340041) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 109171 + ... + 111071.

It is an arithmetic number, because the mean of its divisors is an integer number (9859968).

Almost surely, 2^209340021 is an apocalyptic number.

It is an amenable number.

209340021 is a deficient number, since it is larger than the sum of its proper divisors (106178955).

209340021 is a wasteful number, since it uses less digits than its factorization.

209340021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2033.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 209340021 is about 14468.5873878551. The cubic root of 209340021 is about 593.7688650553.

Adding to 209340021 its reverse (120043902), we get a palindrome (329383923).

The spelling of 209340021 in words is "two hundred nine million, three hundred forty thousand, twenty-one".