20971805 has 8 divisors (see below), whose sum is σ = 25511352. Its totient is φ = 16547328.

The previous prime is 20971799. The next prime is 20971807. The reversal of 20971805 is 50817902.

It can be written as a sum of positive squares in 4 ways, for example, as 4439449 + 16532356 = 2107^2 + 4066^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20971805 - 2⁴ = 20971789 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20971807) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28364 + ... + 29093.

It is an arithmetic number, because the mean of its divisors is an integer number (3188919).

Almost surely, 2^20971805 is an apocalyptic number.

It is an amenable number.

20971805 is a deficient number, since it is larger than the sum of its proper divisors (4539547).

20971805 is an equidigital number, since it uses as much as digits as its factorization.

20971805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57535.

The product of its (nonzero) digits is 5040, while the sum is 32.

The square root of 20971805 is about 4579.4983349708. The cubic root of 20971805 is about 275.7688895329.

The spelling of 20971805 in words is "twenty million, nine hundred seventy-one thousand, eight hundred five".