21775209 has 8 divisors (see below), whose sum is σ = 29581632. Its totient is φ = 14242800.

The previous prime is 21775207. The next prime is 21775219. The reversal of 21775209 is 90257712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21775209 - 2¹ = 21775207 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21775209.

It is not an unprimeable number, because it can be changed into a prime (21775207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 68317 + ... + 68634.

It is an arithmetic number, because the mean of its divisors is an integer number (3697704).

Almost surely, 2^21775209 is an apocalyptic number.

It is an amenable number.

21775209 is a deficient number, since it is larger than the sum of its proper divisors (7806423).

21775209 is a wasteful number, since it uses less digits than its factorization.

21775209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137007.

The product of its (nonzero) digits is 8820, while the sum is 33.

The square root of 21775209 is about 4666.3914323597. The cubic root of 21775209 is about 279.2463106638.

The spelling of 21775209 in words is "twenty-one million, seven hundred seventy-five thousand, two hundred nine".