221801561 has 2 divisors, whose sum is σ = 221801562. Its totient is φ = 221801560.

The previous prime is 221801543. The next prime is 221801579. The reversal of 221801561 is 165108122.

221801561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a balanced prime because it is at equal distance from previous prime (221801543) and next prime (221801579).

It can be written as a sum of positive squares in only one way, i.e., 174741961 + 47059600 = 13219^2 + 6860^2 .

It is a cyclic number.

It is not a de Polignac number, because 221801561 - 2¹⁴ = 221785177 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 221801561.

It is not a weakly prime, because it can be changed into another prime (221801161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110900780 + 110900781.

It is an arithmetic number, because the mean of its divisors is an integer number (110900781).

Almost surely, 2^221801561 is an apocalyptic number.

It is an amenable number.

221801561 is a deficient number, since it is larger than the sum of its proper divisors (1).

221801561 is an equidigital number, since it uses as much as digits as its factorization.

221801561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 960, while the sum is 26.

The square root of 221801561 is about 14893.0037601553. The cubic root of 221801561 is about 605.3244267761.

Adding to 221801561 its reverse (165108122), we get a palindrome (386909683).

The spelling of 221801561 in words is "two hundred twenty-one million, eight hundred one thousand, five hundred sixty-one".