821402021 has 4 divisors (see below), whose sum is σ = 896074944. Its totient is φ = 746729100.

The previous prime is 821401981. The next prime is 821402047. The reversal of 821402021 is 120204128.

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 821402021 - 2⁶ = 821401957 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 821401984 and 821402002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821402051) 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, 37336445 + ... + 37336466.

It is an arithmetic number, because the mean of its divisors is an integer number (224018736).

Almost surely, 2^821402021 is an apocalyptic number.

It is an amenable number.

821402021 is a deficient number, since it is larger than the sum of its proper divisors (74672923).

821402021 is a wasteful number, since it uses less digits than its factorization.

821402021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74672922.

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

The square root of 821402021 is about 28660.1120200183. The cubic root of 821402021 is about 936.5233048629.

Adding to 821402021 its reverse (120204128), we get a palindrome (941606149).

The spelling of 821402021 in words is "eight hundred twenty-one million, four hundred two thousand, twenty-one".