20844721 has 2 divisors, whose sum is σ = 20844722. Its totient is φ = 20844720.

The previous prime is 20844713. The next prime is 20844731. The reversal of 20844721 is 12744802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13359025 + 7485696 = 3655^2 + 2736^2 .

It is a cyclic number.

It is not a de Polignac number, because 20844721 - 2³ = 20844713 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20844721.

It is not a weakly prime, because it can be changed into another prime (20844701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10422360 + 10422361.

It is an arithmetic number, because the mean of its divisors is an integer number (10422361).

Almost surely, 2^20844721 is an apocalyptic number.

It is an amenable number.

20844721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20844721 is an equidigital number, since it uses as much as digits as its factorization.

20844721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3584, while the sum is 28.

The square root of 20844721 is about 4565.6019318377. The cubic root of 20844721 is about 275.2107299384.

The spelling of 20844721 in words is "twenty million, eight hundred forty-four thousand, seven hundred twenty-one".