842878021 has 4 divisors (see below), whose sum is σ = 845988544. Its totient is φ = 839767500.

The previous prime is 842878007. The next prime is 842878051. The reversal of 842878021 is 120878248.

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 842878021 - 2¹³ = 842869829 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 (842878051) 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, 1554855 + ... + 1555396.

It is an arithmetic number, because the mean of its divisors is an integer number (211497136).

Almost surely, 2^842878021 is an apocalyptic number.

It is an amenable number.

842878021 is a deficient number, since it is larger than the sum of its proper divisors (3110523).

842878021 is a wasteful number, since it uses less digits than its factorization.

842878021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3110522.

The product of its (nonzero) digits is 57344, while the sum is 40.

The square root of 842878021 is about 29032.3616159623. The cubic root of 842878021 is about 944.6151567915.

The spelling of 842878021 in words is "eight hundred forty-two million, eight hundred seventy-eight thousand, twenty-one".