20877821 has 2 divisors, whose sum is σ = 20877822. Its totient is φ = 20877820.

The previous prime is 20877797. The next prime is 20877851. The reversal of 20877821 is 12877802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19404025 + 1473796 = 4405^2 + 1214^2 .

It is a cyclic number.

It is not a de Polignac number, because 20877821 - 2⁶ = 20877757 is a prime.

It is a Sophie Germain prime.

It is a Chen 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 (20877851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10438910 + 10438911.

It is an arithmetic number, because the mean of its divisors is an integer number (10438911).

Almost surely, 2^20877821 is an apocalyptic number.

It is an amenable number.

20877821 is a deficient number, since it is larger than the sum of its proper divisors (1).

20877821 is an equidigital number, since it uses as much as digits as its factorization.

20877821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12544, while the sum is 35.

The square root of 20877821 is about 4569.2254266998. The cubic root of 20877821 is about 275.3563248777.

The spelling of 20877821 in words is "twenty million, eight hundred seventy-seven thousand, eight hundred twenty-one".