21009874824409 has 27 divisors (see below), whose sum is σ = 21906383933343. Its totient is φ = 20149225218864.

The previous prime is 21009874824403. The next prime is 21009874824413. The reversal of 21009874824409 is 90442847890012.

The square root of 21009874824409 is 4583653.

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

It can be written as a sum of positive squares in only one way, i.e., 11017068724809 + 9992806099600 = 3319197^2 + 3161140^2 .

It is not a de Polignac number, because 21009874824409 - 2¹¹ = 21009874822361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21009874824403) 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, 23793742282 + ... + 23793743164.

Almost surely, 2^{21009874824409} is an apocalyptic number.

21009874824409 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21009874824409 is the 4583653-rd square number.

21009874824409 is the 2291827-th centered octagonal number.

It is an amenable number.

21009874824409 is a deficient number, since it is larger than the sum of its proper divisors (896509108934).

21009874824409 is an frugal number, since it uses more digits than its factorization.

21009874824409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2182 (or 1091 counting only the distinct ones).

The product of its (nonzero) digits is 9289728, while the sum is 58.

The spelling of 21009874824409 in words is "twenty-one trillion, nine billion, eight hundred seventy-four million, eight hundred twenty-four thousand, four hundred nine".