21083911209 has 27 divisors (see below), whose sum is σ = 31559816613. Its totient is φ = 13563121824.

The previous prime is 21083911153. The next prime is 21083911213. The reversal of 21083911209 is 90211938012.

The square root of 21083911209 is 145203.

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

It can be written as a sum of positive squares in 4 ways, for example, as 70509609 + 21013401600 = 8397^2 + 144960^2 .

It is not a de Polignac number, because 21083911209 - 2²⁷ = 20949693481 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21083916209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 12631827 + ... + 12633495.

Almost surely, 2^21083911209 is an apocalyptic number.

21083911209 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21083911209 is the 145203-rd square number.

21083911209 is the 72602-nd centered octagonal number.

It is an amenable number.

21083911209 is a deficient number, since it is larger than the sum of its proper divisors (10475905404).

21083911209 is an frugal number, since it uses more digits than its factorization.

21083911209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3402 (or 1701 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

Multiplying 21083911209 by its sum of digits (36), we get a square (759020803524 = 871218²).

The spelling of 21083911209 in words is "twenty-one billion, eighty-three million, nine hundred eleven thousand, two hundred nine".