420021821 has 4 divisors (see below), whose sum is σ = 433570944. Its totient is φ = 406472700.

The previous prime is 420021803. The next prime is 420021827. The reversal of 420021821 is 128120024.

It is a happy number.

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 420021821 - 2¹⁴ = 420005437 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 420021793 and 420021802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (420021827) 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, 6774515 + ... + 6774576.

It is an arithmetic number, because the mean of its divisors is an integer number (108392736).

Almost surely, 2^420021821 is an apocalyptic number.

It is an amenable number.

420021821 is a deficient number, since it is larger than the sum of its proper divisors (13549123).

420021821 is a wasteful number, since it uses less digits than its factorization.

420021821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13549122.

The product of its (nonzero) digits is 256, while the sum is 20.

The square root of 420021821 is about 20494.4339028918. The cubic root of 420021821 is about 748.9002079166.

Adding to 420021821 its reverse (128120024), we get a palindrome (548141845).

The spelling of 420021821 in words is "four hundred twenty million, twenty-one thousand, eight hundred twenty-one".