42400021 has 4 divisors (see below), whose sum is σ = 43386112. Its totient is φ = 41413932.

The previous prime is 42400009. The next prime is 42400067. The reversal of 42400021 is 12000424.

42400021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 not a de Polignac number, because 42400021 - 2⁷ = 42399893 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 42399974 and 42400010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (42400081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 492981 + ... + 493066.

It is an arithmetic number, because the mean of its divisors is an integer number (10846528).

Almost surely, 2^42400021 is an apocalyptic number.

It is an amenable number.

42400021 is a deficient number, since it is larger than the sum of its proper divisors (986091).

42400021 is an equidigital number, since it uses as much as digits as its factorization.

42400021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 986090.

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 42400021 is about 6511.5298509644. The cubic root of 42400021 is about 348.7027378219.

Adding to 42400021 its reverse (12000424), we get a palindrome (54400445).

The spelling of 42400021 in words is "forty-two million, four hundred thousand, twenty-one".