21040221 has 4 divisors (see below), whose sum is σ = 28053632. Its totient is φ = 14026812.

The previous prime is 21040213. The next prime is 21040231. The reversal of 21040221 is 12204012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21040221 - 2³ = 21040213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21040197 and 21040206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21040231) 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, 3506701 + ... + 3506706.

It is an arithmetic number, because the mean of its divisors is an integer number (7013408).

Almost surely, 2^21040221 is an apocalyptic number.

It is an amenable number.

21040221 is a deficient number, since it is larger than the sum of its proper divisors (7013411).

21040221 is an equidigital number, since it uses as much as digits as its factorization.

21040221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7013410.

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 21040221 is about 4586.9620665534. The cubic root of 21040221 is about 276.0684429084.

Adding to 21040221 its reverse (12204012), we get a palindrome (33244233).

The spelling of 21040221 in words is "twenty-one million, forty thousand, two hundred twenty-one".