420440021 has 4 divisors (see below), whose sum is σ = 423224544. Its totient is φ = 417655500.

The previous prime is 420440003. The next prime is 420440047. The reversal of 420440021 is 120044024.

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 420440021 - 2²² = 416245717 is a prime.

It is a super-2 number, since 2×420440021² = 353539622516960882, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (420440221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1392035 + ... + 1392336.

It is an arithmetic number, because the mean of its divisors is an integer number (105806136).

Almost surely, 2^420440021 is an apocalyptic number.

It is an amenable number.

420440021 is a deficient number, since it is larger than the sum of its proper divisors (2784523).

420440021 is a wasteful number, since it uses less digits than its factorization.

420440021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2784522.

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 420440021 is about 20504.6341347511. The cubic root of 420440021 is about 749.1486761032.

Adding to 420440021 its reverse (120044024), we get a palindrome (540484045).

The spelling of 420440021 in words is "four hundred twenty million, four hundred forty thousand, twenty-one".