221731613 has 2 divisors, whose sum is σ = 221731614. Its totient is φ = 221731612.

The previous prime is 221731553. The next prime is 221731667. The reversal of 221731613 is 316137122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 210192004 + 11539609 = 14498^2 + 3397^2 .

It is a cyclic number.

It is not a de Polignac number, because 221731613 - 2¹⁴ = 221715229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221739613) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110865806 + 110865807.

It is an arithmetic number, because the mean of its divisors is an integer number (110865807).

Almost surely, 2^221731613 is an apocalyptic number.

It is an amenable number.

221731613 is a deficient number, since it is larger than the sum of its proper divisors (1).

221731613 is an equidigital number, since it uses as much as digits as its factorization.

221731613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1512, while the sum is 26.

The square root of 221731613 is about 14890.6552239987. The cubic root of 221731613 is about 605.2607877819.

Adding to 221731613 its reverse (316137122), we get a palindrome (537868735).

The spelling of 221731613 in words is "two hundred twenty-one million, seven hundred thirty-one thousand, six hundred thirteen".