20570821 has 2 divisors, whose sum is σ = 20570822. Its totient is φ = 20570820.

The previous prime is 20570789. The next prime is 20570839. The reversal of 20570821 is 12807502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14250625 + 6320196 = 3775^2 + 2514^2 .

It is a cyclic number.

It is not a de Polignac number, because 20570821 - 2⁵ = 20570789 is a prime.

It is a super-2 number, since 2×20570821² = 846317353228082, which contains 22 as substring.

It is equal to p_1304467 and since 20570821 and 1304467 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20570861) 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, 10285410 + 10285411.

It is an arithmetic number, because the mean of its divisors is an integer number (10285411).

Almost surely, 2^20570821 is an apocalyptic number.

It is an amenable number.

20570821 is a deficient number, since it is larger than the sum of its proper divisors (1).

20570821 is an equidigital number, since it uses as much as digits as its factorization.

20570821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1120, while the sum is 25.

The square root of 20570821 is about 4535.5066971619. The cubic root of 20570821 is about 273.9999866802. Note that the first 4 decimals are identical.

The spelling of 20570821 in words is "twenty million, five hundred seventy thousand, eight hundred twenty-one".