840280021 has 4 divisors (see below), whose sum is σ = 960320032. Its totient is φ = 720240012.

The previous prime is 840280013. The next prime is 840280033. The reversal of 840280021 is 120082048.

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 840280021 - 2³ = 840280013 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (840280121) 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, 60019995 + ... + 60020008.

It is an arithmetic number, because the mean of its divisors is an integer number (240080008).

Almost surely, 2^840280021 is an apocalyptic number.

It is an amenable number.

840280021 is a deficient number, since it is larger than the sum of its proper divisors (120040011).

840280021 is a wasteful number, since it uses less digits than its factorization.

840280021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120040010.

The product of its (nonzero) digits is 1024, while the sum is 25.

The square root of 840280021 is about 28987.5839110472. The cubic root of 840280021 is about 943.6436299219.

The spelling of 840280021 in words is "eight hundred forty million, two hundred eighty thousand, twenty-one".