21215165 has 8 divisors (see below), whose sum is σ = 25506360. Its totient is φ = 16940032.

The previous prime is 21215147. The next prime is 21215203. The reversal of 21215165 is 56151212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 27556 + 21187609 = 166^2 + 4603^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21215165 - 2⁶ = 21215101 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21215165.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 884 + ... + 6573.

It is an arithmetic number, because the mean of its divisors is an integer number (3188295).

Almost surely, 2^21215165 is an apocalyptic number.

It is an amenable number.

21215165 is a deficient number, since it is larger than the sum of its proper divisors (4291195).

21215165 is an equidigital number, since it uses as much as digits as its factorization.

21215165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8031.

The product of its digits is 600, while the sum is 23.

The square root of 21215165 is about 4605.9922926553. The cubic root of 21215165 is about 276.8314779055.

Adding to 21215165 its reverse (56151212), we get a palindrome (77366377).

The spelling of 21215165 in words is "twenty-one million, two hundred fifteen thousand, one hundred sixty-five".