42549821 has 2 divisors, whose sum is σ = 42549822. Its totient is φ = 42549820.

The previous prime is 42549817. The next prime is 42549823. The reversal of 42549821 is 12894524.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 40896025 + 1653796 = 6395^2 + 1286^2 .

It is a cyclic number.

It is not a de Polignac number, because 42549821 - 2² = 42549817 is a prime.

Together with 42549823, 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 (42549823) 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, 21274910 + 21274911.

It is an arithmetic number, because the mean of its divisors is an integer number (21274911).

Almost surely, 2^42549821 is an apocalyptic number.

It is an amenable number.

42549821 is a deficient number, since it is larger than the sum of its proper divisors (1).

42549821 is an equidigital number, since it uses as much as digits as its factorization.

42549821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23040, while the sum is 35.

The square root of 42549821 is about 6523.0223823010. The cubic root of 42549821 is about 349.1129127294.

The spelling of 42549821 in words is "forty-two million, five hundred forty-nine thousand, eight hundred twenty-one".