221720071 has 4 divisors (see below), whose sum is σ = 222247144. Its totient is φ = 221193000.

The previous prime is 221720047. The next prime is 221720089. The reversal of 221720071 is 170027122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 170027122 = 2 ⋅85013561.

It is a cyclic number.

It is not a de Polignac number, because 221720071 - 2¹⁹ = 221195783 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 (221729071) 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, 262905 + ... + 263746.

It is an arithmetic number, because the mean of its divisors is an integer number (55561786).

Almost surely, 2^221720071 is an apocalyptic number.

221720071 is a deficient number, since it is larger than the sum of its proper divisors (527073).

221720071 is an equidigital number, since it uses as much as digits as its factorization.

221720071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 527072.

The product of its (nonzero) digits is 392, while the sum is 22.

The square root of 221720071 is about 14890.2676604553. The cubic root of 221720071 is about 605.2502855338.

Adding to 221720071 its reverse (170027122), we get a palindrome (391747193).

The spelling of 221720071 in words is "two hundred twenty-one million, seven hundred twenty thousand, seventy-one".