20820821 has 8 divisors (see below), whose sum is σ = 24130944. Its totient is φ = 17594640.

The previous prime is 20820817. The next prime is 20820829. The reversal of 20820821 is 12802802.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20820821 - 2² = 20820817 is a prime.

It is a super-2 number, since 2×20820821² = 867013174228082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20820829) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20450 + ... + 21443.

It is an arithmetic number, because the mean of its divisors is an integer number (3016368).

Almost surely, 2^20820821 is an apocalyptic number.

It is an amenable number.

20820821 is a deficient number, since it is larger than the sum of its proper divisors (3310123).

20820821 is an equidigital number, since it uses as much as digits as its factorization.

20820821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41971.

The product of its (nonzero) digits is 512, while the sum is 23.

The square root of 20820821 is about 4562.9837825703. The cubic root of 20820821 is about 275.1055066235.

The spelling of 20820821 in words is "twenty million, eight hundred twenty thousand, eight hundred twenty-one".