215521 has 2 divisors, whose sum is σ = 215522. Its totient is φ = 215520.

The previous prime is 215507. The next prime is 215531. The reversal of 215521 is 125512.

215521 is nontrivially palindromic in base 14.

215521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 215296 + 225 = 464^2 + 15^2 .

It is a cyclic number.

It is not a de Polignac number, because 215521 - 2⁷ = 215393 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 215495 and 215504.

It is not a weakly prime, because it can be changed into another prime (215531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107760 + 107761.

It is an arithmetic number, because the mean of its divisors is an integer number (107761).

2²¹⁵⁵²¹ is an apocalyptic number.

It is an amenable number.

215521 is a deficient number, since it is larger than the sum of its proper divisors (1).

215521 is an equidigital number, since it uses as much as digits as its factorization.

215521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 100, while the sum is 16.

The square root of 215521 is about 464.2423935834. The cubic root of 215521 is about 59.9556153229.

Subtracting from 215521 its reverse (125512), we obtain a palindrome (90009).

The spelling of 215521 in words is "two hundred fifteen thousand, five hundred twenty-one".