221212405 has 8 divisors (see below), whose sum is σ = 265568184. Its totient is φ = 176894400.

The previous prime is 221212361. The next prime is 221212423. The reversal of 221212405 is 504212122.

It can be written as a sum of positive squares in 4 ways, for example, as 6355441 + 214856964 = 2521^2 + 14658^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 221212405 - 2¹¹ = 221210357 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5635 + ... + 21775.

It is an arithmetic number, because the mean of its divisors is an integer number (33196023).

Almost surely, 2^221212405 is an apocalyptic number.

It is an amenable number.

221212405 is a deficient number, since it is larger than the sum of its proper divisors (44355779).

221212405 is a wasteful number, since it uses less digits than its factorization.

221212405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18887.

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 221212405 is about 14873.2109848546. The cubic root of 221212405 is about 604.7879911931.

Adding to 221212405 its reverse (504212122), we get a palindrome (725424527).

The spelling of 221212405 in words is "two hundred twenty-one million, two hundred twelve thousand, four hundred five".