221234821 has 4 divisors (see below), whose sum is σ = 234248652. Its totient is φ = 208220992.

The previous prime is 221234813. The next prime is 221234831. The reversal of 221234821 is 128432122.

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 206496900 + 14737921 = 14370^2 + 3839^2 .

It is a cyclic number.

It is not a de Polignac number, because 221234821 - 2³ = 221234813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221234801) 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, 6506890 + ... + 6506923.

It is an arithmetic number, because the mean of its divisors is an integer number (58562163).

Almost surely, 2^221234821 is an apocalyptic number.

It is an amenable number.

221234821 is a deficient number, since it is larger than the sum of its proper divisors (13013831).

221234821 is a wasteful number, since it uses less digits than its factorization.

221234821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13013830.

The product of its digits is 1536, while the sum is 25.

The square root of 221234821 is about 14873.9645353887. The cubic root of 221234821 is about 604.8084187240.

Adding to 221234821 its reverse (128432122), we get a palindrome (349666943).

The spelling of 221234821 in words is "two hundred twenty-one million, two hundred thirty-four thousand, eight hundred twenty-one".