20976821 has 2 divisors, whose sum is σ = 20976822. Its totient is φ = 20976820.

The previous prime is 20976797. The next prime is 20976833. The reversal of 20976821 is 12867902.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20376196 + 600625 = 4514^2 + 775^2 .

It is a cyclic number.

It is not a de Polignac number, because 20976821 - 2¹⁰ = 20975797 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20976121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10488410 + 10488411.

It is an arithmetic number, because the mean of its divisors is an integer number (10488411).

Almost surely, 2^20976821 is an apocalyptic number.

It is an amenable number.

20976821 is a deficient number, since it is larger than the sum of its proper divisors (1).

20976821 is an equidigital number, since it uses as much as digits as its factorization.

20976821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 20976821 is about 4580.0459604681. The cubic root of 20976821 is about 275.7908737554.

The spelling of 20976821 in words is "twenty million, nine hundred seventy-six thousand, eight hundred twenty-one".