900021 has 4 divisors (see below), whose sum is σ = 1200032. Its totient is φ = 600012.

The previous prime is 900019. The next prime is 900037. The reversal of 900021 is 120009.

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 not a de Polignac number, because 900021 - 2¹ = 900019 is a prime.

It is a D-number.

It is a Duffinian number.

900021 is a lucky number.

It is a nialpdrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (900001) 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, 150001 + ... + 150006.

It is an arithmetic number, because the mean of its divisors is an integer number (300008).

2⁹⁰⁰⁰²¹ is an apocalyptic number.

It is an amenable number.

900021 is a deficient number, since it is larger than the sum of its proper divisors (300011).

900021 is a wasteful number, since it uses less digits than its factorization.

900021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300010.

The product of its (nonzero) digits is 18, while the sum is 12.

The square root of 900021 is about 948.6943659578. The cubic root of 900021 is about 96.5496893909.

Subtracting from 900021 its sum of digits (12), we obtain a palindrome (900009).

The spelling of 900021 in words is "nine hundred thousand, twenty-one".