221721073 has 4 divisors (see below), whose sum is σ = 253395520. Its totient is φ = 190046628.

The previous prime is 221721067. The next prime is 221721103. The reversal of 221721073 is 370127122.

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, and also an emirpimes, since its reverse is a distinct semiprime: 370127122 = 2 ⋅185063561.

It is a cyclic number.

It is not a de Polignac number, because 221721073 - 2⁵ = 221721041 is a prime.

It is not an unprimeable number, because it can be changed into a prime (221721473) 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, 15837213 + ... + 15837226.

It is an arithmetic number, because the mean of its divisors is an integer number (63348880).

Almost surely, 2^221721073 is an apocalyptic number.

It is an amenable number.

221721073 is a deficient number, since it is larger than the sum of its proper divisors (31674447).

221721073 is an equidigital number, since it uses as much as digits as its factorization.

221721073 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31674446.

The product of its (nonzero) digits is 1176, while the sum is 25.

The square root of 221721073 is about 14890.3013065552. The cubic root of 221721073 is about 605.2511972839.

Adding to 221721073 its reverse (370127122), we get a palindrome (591848195).

The spelling of 221721073 in words is "two hundred twenty-one million, seven hundred twenty-one thousand, seventy-three".