221136521 has 4 divisors (see below), whose sum is σ = 221770500. Its totient is φ = 220502544.

The previous prime is 221136479. The next prime is 221136523. The reversal of 221136521 is 125631122.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 168065296 + 53071225 = 12964^2 + 7285^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221136521 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (221136523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 316466 + ... + 317163.

It is an arithmetic number, because the mean of its divisors is an integer number (55442625).

Almost surely, 2^221136521 is an apocalyptic number.

It is an amenable number.

221136521 is a deficient number, since it is larger than the sum of its proper divisors (633979).

221136521 is an equidigital number, since it uses as much as digits as its factorization.

221136521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 633978.

The product of its digits is 720, while the sum is 23.

The square root of 221136521 is about 14870.6597365416. The cubic root of 221136521 is about 604.7188284343.

Adding to 221136521 its reverse (125631122), we get a palindrome (346767643).

The spelling of 221136521 in words is "two hundred twenty-one million, one hundred thirty-six thousand, five hundred twenty-one".