221721253 has 4 divisors (see below), whose sum is σ = 238776748. Its totient is φ = 204665760.

The previous prime is 221721251. The next prime is 221721257. The reversal of 221721253 is 352127122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 352127122 = 2 ⋅176063561.

It can be written as a sum of positive squares in 2 ways, for example, as 47032164 + 174689089 = 6858^2 + 13217^2 .

It is not a de Polignac number, because 221721253 - 2¹ = 221721251 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221721251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8527728 + ... + 8527753.

It is an arithmetic number, because the mean of its divisors is an integer number (59694187).

Almost surely, 2^221721253 is an apocalyptic number.

It is an amenable number.

221721253 is a deficient number, since it is larger than the sum of its proper divisors (17055495).

221721253 is a wasteful number, since it uses less digits than its factorization.

221721253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17055494.

The product of its digits is 1680, while the sum is 25.

The square root of 221721253 is about 14890.3073507567. The cubic root of 221721253 is about 605.2513610710.

Adding to 221721253 its reverse (352127122), we get a palindrome (573848375).

The spelling of 221721253 in words is "two hundred twenty-one million, seven hundred twenty-one thousand, two hundred fifty-three".