820421 has 4 divisors (see below), whose sum is σ = 937632. Its totient is φ = 703212.

The previous prime is 820411. The next prime is 820427. The reversal of 820421 is 124028.

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 a de Polignac number, because none of the positive numbers 2^k-820421 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 820421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820427) 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, 58595 + ... + 58608.

It is an arithmetic number, because the mean of its divisors is an integer number (234408).

2⁸²⁰⁴²¹ is an apocalyptic number.

It is an amenable number.

820421 is a deficient number, since it is larger than the sum of its proper divisors (117211).

820421 is a wasteful number, since it uses less digits than its factorization.

820421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117210.

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 820421 is about 905.7709423469. The cubic root of 820421 is about 93.6150318591.

Adding to 820421 its reverse (124028), we get a palindrome (944449).

The spelling of 820421 in words is "eight hundred twenty thousand, four hundred twenty-one".