242021821 has 2 divisors, whose sum is σ = 242021822. Its totient is φ = 242021820.

The previous prime is 242021779. The next prime is 242021833. The reversal of 242021821 is 128120242.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 223652025 + 18369796 = 14955^2 + 4286^2 .

It is a cyclic number.

It is not a de Polignac number, because 242021821 - 2¹⁵ = 241989053 is a prime.

It is a Chen prime.

It is equal to p_13266400 and since 242021821 and 13266400 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 242021792 and 242021801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (242021891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 121010910 + 121010911.

It is an arithmetic number, because the mean of its divisors is an integer number (121010911).

Almost surely, 2^242021821 is an apocalyptic number.

It is an amenable number.

242021821 is a deficient number, since it is larger than the sum of its proper divisors (1).

242021821 is an equidigital number, since it uses as much as digits as its factorization.

242021821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 512, while the sum is 22.

The square root of 242021821 is about 15557.0505237979. The cubic root of 242021821 is about 623.1866981058.

The spelling of 242021821 in words is "two hundred forty-two million, twenty-one thousand, eight hundred twenty-one".