42806021 has 4 divisors (see below), whose sum is σ = 42838572. Its totient is φ = 42773472.

The previous prime is 42805999. The next prime is 42806041. The reversal of 42806021 is 12060824.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 38925121 + 3880900 = 6239^2 + 1970^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42806021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42806041) 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 in 3 ways as a sum of consecutive naturals, for example, 14216 + ... + 16961.

It is an arithmetic number, because the mean of its divisors is an integer number (10709643).

Almost surely, 2^42806021 is an apocalyptic number.

It is an amenable number.

42806021 is a deficient number, since it is larger than the sum of its proper divisors (32551).

42806021 is a wasteful number, since it uses less digits than its factorization.

42806021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32550.

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 42806021 is about 6542.6310456880. The cubic root of 42806021 is about 349.8122012921.

Adding to 42806021 its reverse (12060824), we get a palindrome (54866845).

It can be divided in two parts, 4280 and 6021, that added together give a palindrome (10301).

The spelling of 42806021 in words is "forty-two million, eight hundred six thousand, twenty-one".