21435221 has 4 divisors (see below), whose sum is σ = 21489612. Its totient is φ = 21380832.

The previous prime is 21435163. The next prime is 21435233. The reversal of 21435221 is 12253412.

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 18748900 + 2686321 = 4330^2 + 1639^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21435221 is a prime.

It is a super-4 number, since 4×21435221⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21435193 and 21435202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21434221) 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, 26600 + ... + 27393.

It is an arithmetic number, because the mean of its divisors is an integer number (5372403).

Almost surely, 2^21435221 is an apocalyptic number.

It is an amenable number.

21435221 is a deficient number, since it is larger than the sum of its proper divisors (54391).

21435221 is an equidigital number, since it uses as much as digits as its factorization.

21435221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54390.

The product of its digits is 480, while the sum is 20.

The square root of 21435221 is about 4629.8186789549. The cubic root of 21435221 is about 277.7853396993.

Adding to 21435221 its reverse (12253412), we get a palindrome (33688633).

The spelling of 21435221 in words is "twenty-one million, four hundred thirty-five thousand, two hundred twenty-one".