221221213421 has 24 divisors (see below), whose sum is σ = 262154649120. Its totient is φ = 185045341536.

The previous prime is 221221213373. The next prime is 221221213501. The reversal of 221221213421 is 124312122122.

It is not a de Polignac number, because 221221213421 - 2¹⁰ = 221221212397 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221221213621) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 715871 + ... + 977196.

It is an arithmetic number, because the mean of its divisors is an integer number (10923110380).

Almost surely, 2^221221213421 is an apocalyptic number.

It is an amenable number.

221221213421 is a deficient number, since it is larger than the sum of its proper divisors (40933435699).

221221213421 is a wasteful number, since it uses less digits than its factorization.

221221213421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1693145 (or 1693122 counting only the distinct ones).

The product of its digits is 768, while the sum is 23.

Adding to 221221213421 its reverse (124312122122), we get a palindrome (345533335543).

The spelling of 221221213421 in words is "two hundred twenty-one billion, two hundred twenty-one million, two hundred thirteen thousand, four hundred twenty-one".