221215421 has 8 divisors (see below), whose sum is σ = 253439040. Its totient is φ = 189147168.

The previous prime is 221215399. The next prime is 221215429. The reversal of 221215421 is 124512122.

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

It is not a de Polignac number, because 221215421 - 2¹⁸ = 220953277 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 221215393 and 221215402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221215429) by changing a digit.

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, 35771 + ... + 41496.

It is an arithmetic number, because the mean of its divisors is an integer number (31679880).

Almost surely, 2^221215421 is an apocalyptic number.

It is an amenable number.

221215421 is a deficient number, since it is larger than the sum of its proper divisors (32223619).

221215421 is an equidigital number, since it uses as much as digits as its factorization.

221215421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77683.

The product of its digits is 320, while the sum is 20.

The square root of 221215421 is about 14873.3123748545. The cubic root of 221215421 is about 604.7907397314.

Adding to 221215421 its reverse (124512122), we get a palindrome (345727543).

The spelling of 221215421 in words is "two hundred twenty-one million, two hundred fifteen thousand, four hundred twenty-one".