21228231 has 4 divisors (see below), whose sum is σ = 28304312. Its totient is φ = 14152152.

The previous prime is 21228227. The next prime is 21228247. The reversal of 21228231 is 13282212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21228231 - 2² = 21228227 is a prime.

It is a super-2 number, since 2×21228231² = 901275582778722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21228198 and 21228207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21228331) 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, 3538036 + ... + 3538041.

It is an arithmetic number, because the mean of its divisors is an integer number (7076078).

Almost surely, 2^21228231 is an apocalyptic number.

21228231 is a deficient number, since it is larger than the sum of its proper divisors (7076081).

21228231 is an equidigital number, since it uses as much as digits as its factorization.

21228231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7076080.

The product of its digits is 384, while the sum is 21.

The square root of 21228231 is about 4607.4104440564. The cubic root of 21228231 is about 276.8882979174. Note that the first 3 decimals are identical.

The spelling of 21228231 in words is "twenty-one million, two hundred twenty-eight thousand, two hundred thirty-one".