21321215 has 8 divisors (see below), whose sum is σ = 25743408. Its totient is φ = 16951680.

The previous prime is 21321203. The next prime is 21321217. The reversal of 21321215 is 51212312.

It is a happy number.

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

It is not a de Polignac number, because 21321215 - 2⁴ = 21321199 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 21321193 and 21321202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321217) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12266 + ... + 13895.

It is an arithmetic number, because the mean of its divisors is an integer number (3217926).

Almost surely, 2^21321215 is an apocalyptic number.

21321215 is a deficient number, since it is larger than the sum of its proper divisors (4422193).

21321215 is a wasteful number, since it uses less digits than its factorization.

21321215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26329.

The product of its digits is 120, while the sum is 17.

The square root of 21321215 is about 4617.4901191015. The cubic root of 21321215 is about 277.2919848995.

Adding to 21321215 its reverse (51212312), we get a palindrome (72533527).

The spelling of 21321215 in words is "twenty-one million, three hundred twenty-one thousand, two hundred fifteen".