221720549 has 2 divisors, whose sum is σ = 221720550. Its totient is φ = 221720548.

The previous prime is 221720507. The next prime is 221720561. The reversal of 221720549 is 945027122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 187416100 + 34304449 = 13690^2 + 5857^2 .

It is a cyclic number.

It is not a de Polignac number, because 221720549 - 2⁸ = 221720293 is a prime.

It is a super-2 number, since 2×221720549² = 98320003697722802, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221722549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110860274 + 110860275.

It is an arithmetic number, because the mean of its divisors is an integer number (110860275).

Almost surely, 2^221720549 is an apocalyptic number.

It is an amenable number.

221720549 is a deficient number, since it is larger than the sum of its proper divisors (1).

221720549 is an equidigital number, since it uses as much as digits as its factorization.

221720549 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 221720549 is about 14890.2837111991. The cubic root of 221720549 is about 605.2507204808.

The spelling of 221720549 in words is "two hundred twenty-one million, seven hundred twenty thousand, five hundred forty-nine".