428220021 has 16 divisors (see below), whose sum is σ = 605059200. Its totient is φ = 268459008.

The previous prime is 428220017. The next prime is 428220041. The reversal of 428220021 is 120022824.

It is a happy number.

It is not a de Polignac number, because 428220021 - 2² = 428220017 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 428220021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (428220011) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 73120 + ... + 78758.

It is an arithmetic number, because the mean of its divisors is an integer number (37816200).

Almost surely, 2^428220021 is an apocalyptic number.

It is an amenable number.

428220021 is a deficient number, since it is larger than the sum of its proper divisors (176839179).

428220021 is a wasteful number, since it uses less digits than its factorization.

428220021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7148.

The product of its (nonzero) digits is 512, while the sum is 21.

The square root of 428220021 is about 20693.4777405829. The cubic root of 428220021 is about 753.7413181292.

Adding to 428220021 its reverse (120022824), we get a palindrome (548242845).

The spelling of 428220021 in words is "four hundred twenty-eight million, two hundred twenty thousand, twenty-one".