20829821 has 2 divisors, whose sum is σ = 20829822. Its totient is φ = 20829820.

The previous prime is 20829749. The next prime is 20829839. The reversal of 20829821 is 12892802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20748025 + 81796 = 4555^2 + 286^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20829821 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20829841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10414910 + 10414911.

It is an arithmetic number, because the mean of its divisors is an integer number (10414911).

Almost surely, 2^20829821 is an apocalyptic number.

It is an amenable number.

20829821 is a deficient number, since it is larger than the sum of its proper divisors (1).

20829821 is an equidigital number, since it uses as much as digits as its factorization.

20829821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 20829821 is about 4563.9698728191. The cubic root of 20829821 is about 275.1451399133.

The spelling of 20829821 in words is "twenty million, eight hundred twenty-nine thousand, eight hundred twenty-one".