21263221 has 8 divisors (see below), whose sum is σ = 24634304. Its totient is φ = 17975520.

The previous prime is 21263213. The next prime is 21263233. The reversal of 21263221 is 12236212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21263221 - 2³ = 21263213 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 (21263621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20295 + ... + 21316.

It is an arithmetic number, because the mean of its divisors is an integer number (3079288).

Almost surely, 2^21263221 is an apocalyptic number.

It is an amenable number.

21263221 is a deficient number, since it is larger than the sum of its proper divisors (3371083).

21263221 is an equidigital number, since it uses as much as digits as its factorization.

21263221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41691.

The product of its digits is 288, while the sum is 19.

The square root of 21263221 is about 4611.2060244582. The cubic root of 21263221 is about 277.0403439263.

Adding to 21263221 its reverse (12236212), we get a palindrome (33499433).

The spelling of 21263221 in words is "twenty-one million, two hundred sixty-three thousand, two hundred twenty-one".