221821385 has 4 divisors (see below), whose sum is σ = 266185668. Its totient is φ = 177457104.

The previous prime is 221821381. The next prime is 221821387. The reversal of 221821385 is 583128122.

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 55591936 + 166229449 = 7456^2 + 12893^2 .

It is a cyclic number.

It is not a de Polignac number, because 221821385 - 2² = 221821381 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221821381) 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, 22182134 + ... + 22182143.

It is an arithmetic number, because the mean of its divisors is an integer number (66546417).

Almost surely, 2^221821385 is an apocalyptic number.

It is an amenable number.

221821385 is a deficient number, since it is larger than the sum of its proper divisors (44364283).

221821385 is an equidigital number, since it uses as much as digits as its factorization.

221821385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44364282.

The product of its digits is 7680, while the sum is 32.

The square root of 221821385 is about 14893.6692926894. The cubic root of 221821385 is about 605.3424603040.

The spelling of 221821385 in words is "two hundred twenty-one million, eight hundred twenty-one thousand, three hundred eighty-five".