20628821 has 2 divisors, whose sum is σ = 20628822. Its totient is φ = 20628820.

The previous prime is 20628809. The next prime is 20628823. The reversal of 20628821 is 12882602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15288100 + 5340721 = 3910^2 + 2311^2 .

It is a cyclic number.

It is not a de Polignac number, because 20628821 - 2⁶ = 20628757 is a prime.

Together with 20628823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20628823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10314410 + 10314411.

It is an arithmetic number, because the mean of its divisors is an integer number (10314411).

Almost surely, 2^20628821 is an apocalyptic number.

It is an amenable number.

20628821 is a deficient number, since it is larger than the sum of its proper divisors (1).

20628821 is an equidigital number, since it uses as much as digits as its factorization.

20628821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 20628821 is about 4541.8961899189. The cubic root of 20628821 is about 274.2572618857.

The spelling of 20628821 in words is "twenty million, six hundred twenty-eight thousand, eight hundred twenty-one".