221307561 has 12 divisors (see below), whose sum is σ = 321184240. Its totient is φ = 146837880.

The previous prime is 221307557. The next prime is 221307571. The reversal of 221307561 is 165703122.

It is a happy number.

It is not a de Polignac number, because 221307561 - 2² = 221307557 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (221307511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 56371 + ... + 60168.

Almost surely, 2^221307561 is an apocalyptic number.

It is an amenable number.

221307561 is a deficient number, since it is larger than the sum of its proper divisors (99876679).

221307561 is a wasteful number, since it uses less digits than its factorization.

221307561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 116756 (or 116753 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 27.

The square root of 221307561 is about 14876.4095466615. The cubic root of 221307561 is about 604.8746966325.

The spelling of 221307561 in words is "two hundred twenty-one million, three hundred seven thousand, five hundred sixty-one".