21595184209 has 3 divisors (see below), whose sum is σ = 21595331163. Its totient is φ = 21595037256.

The previous prime is 21595184207. The next prime is 21595184213. The reversal of 21595184209 is 90248159512.

It is a happy number.

The square root of 21595184209 is 146953.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 358534225 + 21236649984 = 18935^2 + 145728^2 .

It is not a de Polignac number, because 21595184209 - 2¹ = 21595184207 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21595184203) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 73477 + ... + 220429.

It is an arithmetic number, because the mean of its divisors is an integer number (7198443721).

Almost surely, 2^21595184209 is an apocalyptic number.

21595184209 is the 146953-rd square number.

21595184209 is the 73477-th centered octagonal number.

It is an amenable number.

21595184209 is a deficient number, since it is larger than the sum of its proper divisors (146954).

21595184209 is an frugal number, since it uses more digits than its factorization.

21595184209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 293906 (or 146953 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 46.

The spelling of 21595184209 in words is "twenty-one billion, five hundred ninety-five million, one hundred eighty-four thousand, two hundred nine".