215421 has 4 divisors (see below), whose sum is σ = 287232. Its totient is φ = 143612.

The previous prime is 215417. The next prime is 215443. The reversal of 215421 is 124512.

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 215421 - 2² = 215417 is a prime.

It is a D-number.

215421 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 215421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215461) 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, 35901 + ... + 35906.

It is an arithmetic number, because the mean of its divisors is an integer number (71808).

2²¹⁵⁴²¹ is an apocalyptic number.

It is an amenable number.

215421 is a deficient number, since it is larger than the sum of its proper divisors (71811).

215421 is an equidigital number, since it uses as much as digits as its factorization.

215421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71810.

The product of its digits is 80, while the sum is 15.

The square root of 215421 is about 464.1346787302. The cubic root of 215421 is about 59.9463409149.

Adding to 215421 its reverse (124512), we get a palindrome (339933).

Subtracting from 215421 its reverse (124512), we obtain a palindrome (90909).

It can be divided in two parts, 215 and 421, that added together give a palindrome (636).

The spelling of 215421 in words is "two hundred fifteen thousand, four hundred twenty-one".