421128821 has 4 divisors (see below), whose sum is σ = 424202892. Its totient is φ = 418054752.

The previous prime is 421128817. The next prime is 421128823. The reversal of 421128821 is 128821124.

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 103754596 + 317374225 = 10186^2 + 17815^2 .

It is a cyclic number.

It is not a de Polignac number, because 421128821 - 2² = 421128817 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 (421128823) 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, 1536830 + ... + 1537103.

It is an arithmetic number, because the mean of its divisors is an integer number (106050723).

Almost surely, 2^421128821 is an apocalyptic number.

It is an amenable number.

421128821 is a deficient number, since it is larger than the sum of its proper divisors (3074071).

421128821 is a wasteful number, since it uses less digits than its factorization.

421128821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3074070.

The product of its digits is 2048, while the sum is 29.

The square root of 421128821 is about 20521.4234642726. The cubic root of 421128821 is about 749.5575588977.

Adding to 421128821 its reverse (128821124), we get a palindrome (549949945).

The spelling of 421128821 in words is "four hundred twenty-one million, one hundred twenty-eight thousand, eight hundred twenty-one".