221553561 has 4 divisors (see below), whose sum is σ = 295404752. Its totient is φ = 147702372.

The previous prime is 221553557. The next prime is 221553569. The reversal of 221553561 is 165355122.

It is a happy number.

221553561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 not a de Polignac number, because 221553561 - 2² = 221553557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221553569) 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, 36925591 + ... + 36925596.

It is an arithmetic number, because the mean of its divisors is an integer number (73851188).

Almost surely, 2^221553561 is an apocalyptic number.

It is an amenable number.

221553561 is a deficient number, since it is larger than the sum of its proper divisors (73851191).

221553561 is an equidigital number, since it uses as much as digits as its factorization.

221553561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73851190.

The product of its digits is 9000, while the sum is 30.

The square root of 221553561 is about 14884.6753743573. The cubic root of 221553561 is about 605.0987348818.

The spelling of 221553561 in words is "two hundred twenty-one million, five hundred fifty-three thousand, five hundred sixty-one".