21215273 has 4 divisors (see below), whose sum is σ = 21300048. Its totient is φ = 21130500.

The previous prime is 21215263. The next prime is 21215287. The reversal of 21215273 is 37251212.

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 a cyclic number.

It is not a de Polignac number, because 21215273 - 2⁸ = 21215017 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21215203) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42011 + ... + 42512.

It is an arithmetic number, because the mean of its divisors is an integer number (5325012).

Almost surely, 2^21215273 is an apocalyptic number.

It is an amenable number.

21215273 is a deficient number, since it is larger than the sum of its proper divisors (84775).

21215273 is an equidigital number, since it uses as much as digits as its factorization.

21215273 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84774.

The product of its digits is 840, while the sum is 23.

The square root of 21215273 is about 4606.0040164985. The cubic root of 21215273 is about 276.8319476599.

Adding to 21215273 its reverse (37251212), we get a palindrome (58466485).

The spelling of 21215273 in words is "twenty-one million, two hundred fifteen thousand, two hundred seventy-three".