20708821 has 12 divisors (see below), whose sum is σ = 24343788. Its totient is φ = 17563392.

The previous prime is 20708819. The next prime is 20708833. The reversal of 20708821 is 12880702.

It can be written as a sum of positive squares in 2 ways, for example, as 17056900 + 3651921 = 4130^2 + 1911^2 .

It is not a de Polignac number, because 20708821 - 2¹ = 20708819 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20708821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20708851) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2575 + ... + 6931.

It is an arithmetic number, because the mean of its divisors is an integer number (2028649).

Almost surely, 2^20708821 is an apocalyptic number.

It is an amenable number.

20708821 is a deficient number, since it is larger than the sum of its proper divisors (3634967).

20708821 is an equidigital number, since it uses as much as digits as its factorization.

20708821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4468 (or 4461 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 28.

The square root of 20708821 is about 4550.6945623718. The cubic root of 20708821 is about 274.6113341411.

The spelling of 20708821 in words is "twenty million, seven hundred eight thousand, eight hundred twenty-one".