42809021 has 4 divisors (see below), whose sum is σ = 43033344. Its totient is φ = 42584700.

The previous prime is 42808991. The next prime is 42809027. The reversal of 42809021 is 12090824.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-42809021 is a prime.

It is a super-2 number, since 2×42809021² = 3665224557956882, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42809027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111875 + ... + 112256.

It is an arithmetic number, because the mean of its divisors is an integer number (10758336).

Almost surely, 2^42809021 is an apocalyptic number.

It is an amenable number.

42809021 is a deficient number, since it is larger than the sum of its proper divisors (224323).

42809021 is a wasteful number, since it uses less digits than its factorization.

42809021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 224322.

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 42809021 is about 6542.8603072357. The cubic root of 42809021 is about 349.8203731339.

Adding to 42809021 its reverse (12090824), we get a palindrome (54899845).

The spelling of 42809021 in words is "forty-two million, eight hundred nine thousand, twenty-one".