42000821 has 2 divisors, whose sum is σ = 42000822. Its totient is φ = 42000820.

The previous prime is 42000799. The next prime is 42000841. The reversal of 42000821 is 12800024.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 39564100 + 2436721 = 6290^2 + 1561^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42000821 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 42000821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (42000841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 21000410 + 21000411.

It is an arithmetic number, because the mean of its divisors is an integer number (21000411).

Almost surely, 2^42000821 is an apocalyptic number.

It is an amenable number.

42000821 is a deficient number, since it is larger than the sum of its proper divisors (1).

42000821 is an equidigital number, since it uses as much as digits as its factorization.

42000821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 42000821 is about 6480.8040396235. The cubic root of 42000821 is about 347.6049294087.

Adding to 42000821 its reverse (12800024), we get a palindrome (54800845).

The spelling of 42000821 in words is "forty-two million, eight hundred twenty-one", and thus it is an aban number.