21141221 has 4 divisors (see below), whose sum is σ = 21154092. Its totient is φ = 21128352.

The previous prime is 21141161. The next prime is 21141227. The reversal of 21141221 is 12214112.

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 17850625 + 3290596 = 4225^2 + 1814^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21141221 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21141196 and 21141205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21141227) 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, 3536 + ... + 7401.

It is an arithmetic number, because the mean of its divisors is an integer number (5288523).

Almost surely, 2^21141221 is an apocalyptic number.

It is an amenable number.

21141221 is a deficient number, since it is larger than the sum of its proper divisors (12871).

21141221 is a wasteful number, since it uses less digits than its factorization.

21141221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12870.

The product of its digits is 32, while the sum is 14.

The square root of 21141221 is about 4597.9583512685. The cubic root of 21141221 is about 276.5094778134.

Adding to 21141221 its product of digits (32), we get a triangular number (21141253 = T₆₅₀₂).

Adding to 21141221 its reverse (12214112), we get a palindrome (33355333).

The spelling of 21141221 in words is "twenty-one million, one hundred forty-one thousand, two hundred twenty-one".