21056071783609 has 4 divisors (see below), whose sum is σ = 21056945612404. Its totient is φ = 21055197954816.

The previous prime is 21056071783597. The next prime is 21056071783667. The reversal of 21056071783609 is 90638717065012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10948422145600 + 10107649638009 = 3308840^2 + 3179253^2 .

It is a cyclic number.

It is not a de Polignac number, because 21056071783609 - 2²⁷ = 21055937565881 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21056071783609.

It is not an unprimeable number, because it can be changed into a prime (21056071783009) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 436878252 + ... + 436926445.

It is an arithmetic number, because the mean of its divisors is an integer number (5264236403101).

Almost surely, 2^{21056071783609} is an apocalyptic number.

It is an amenable number.

21056071783609 is a deficient number, since it is larger than the sum of its proper divisors (873828795).

21056071783609 is an equidigital number, since it uses as much as digits as its factorization.

21056071783609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 873828794.

The product of its (nonzero) digits is 3810240, while the sum is 55.

The spelling of 21056071783609 in words is "twenty-one trillion, fifty-six billion, seventy-one million, seven hundred eighty-three thousand, six hundred nine".