20814821 has 6 divisors (see below), whose sum is σ = 20986770. Its totient is φ = 20644256.

The previous prime is 20814811. The next prime is 20814863. The reversal of 20814821 is 12841802.

It can be written as a sum of positive squares in 3 ways, for example, as 474721 + 20340100 = 689^2 + 4510^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20814821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20814811) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 18215 + ... + 19323.

It is an arithmetic number, because the mean of its divisors is an integer number (3497795).

Almost surely, 2^20814821 is an apocalyptic number.

It is an amenable number.

20814821 is a deficient number, since it is larger than the sum of its proper divisors (171949).

20814821 is an equidigital number, since it uses as much as digits as its factorization.

20814821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1383 (or 1246 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 20814821 is about 4562.3262706650. The cubic root of 20814821 is about 275.0790780848.

The spelling of 20814821 in words is "twenty million, eight hundred fourteen thousand, eight hundred twenty-one".