221431561 has 4 divisors (see below), whose sum is σ = 238464772. Its totient is φ = 204398352.

The previous prime is 221431541. The next prime is 221431577. The reversal of 221431561 is 165134122.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 34152336 + 187279225 = 5844^2 + 13685^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221431561 is a prime.

It is not an unprimeable number, because it can be changed into a prime (221431531) 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 3 ways as a sum of consecutive naturals, for example, 8516586 + ... + 8516611.

It is an arithmetic number, because the mean of its divisors is an integer number (59616193).

Almost surely, 2^221431561 is an apocalyptic number.

It is an amenable number.

221431561 is a deficient number, since it is larger than the sum of its proper divisors (17033211).

221431561 is a wasteful number, since it uses less digits than its factorization.

221431561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17033210.

The product of its digits is 1440, while the sum is 25.

The square root of 221431561 is about 14880.5766353324. The cubic root of 221431561 is about 604.9876472218.

Adding to 221431561 its reverse (165134122), we get a palindrome (386565683).

The spelling of 221431561 in words is "two hundred twenty-one million, four hundred thirty-one thousand, five hundred sixty-one".