21072221 has 8 divisors (see below), whose sum is σ = 21350400. Its totient is φ = 20796048.

The previous prime is 21072211. The next prime is 21072229. The reversal of 21072221 is 12227012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21072221 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21072221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21072229) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34880 + ... + 35478.

It is an arithmetic number, because the mean of its divisors is an integer number (2668800).

Almost surely, 2^21072221 is an apocalyptic number.

It is an amenable number.

21072221 is a deficient number, since it is larger than the sum of its proper divisors (278179).

21072221 is a wasteful number, since it uses less digits than its factorization.

21072221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1003.

The product of its (nonzero) digits is 112, while the sum is 17.

The square root of 21072221 is about 4590.4488887254. The cubic root of 21072221 is about 276.2083291977.

Adding to 21072221 its reverse (12227012), we get a palindrome (33299233).

The spelling of 21072221 in words is "twenty-one million, seventy-two thousand, two hundred twenty-one".