221720557 has 4 divisors (see below), whose sum is σ = 233390080. Its totient is φ = 210051036.

The previous prime is 221720549. The next prime is 221720561. The reversal of 221720557 is 755027122.

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.

It is a cyclic number.

It is not a de Polignac number, because 221720557 - 2³ = 221720549 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 (221720507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5834733 + ... + 5834770.

It is an arithmetic number, because the mean of its divisors is an integer number (58347520).

Almost surely, 2^221720557 is an apocalyptic number.

It is an amenable number.

221720557 is a deficient number, since it is larger than the sum of its proper divisors (11669523).

221720557 is a wasteful number, since it uses less digits than its factorization.

221720557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11669522.

The product of its (nonzero) digits is 9800, while the sum is 31.

The square root of 221720557 is about 14890.2839798306. The cubic root of 221720557 is about 605.2507277602.

Adding to 221720557 its reverse (755027122), we get a palindrome (976747679).

The spelling of 221720557 in words is "two hundred twenty-one million, seven hundred twenty thousand, five hundred fifty-seven".