21016221 has 8 divisors (see below), whose sum is σ = 28044480. Its totient is φ = 13999392.

The previous prime is 21016217. The next prime is 21016241. The reversal of 21016221 is 12261012.

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

It is not a de Polignac number, because 21016221 - 2² = 21016217 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21016221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21016201) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3385 + ... + 7313.

It is an arithmetic number, because the mean of its divisors is an integer number (3505560).

Almost surely, 2^21016221 is an apocalyptic number.

It is an amenable number.

21016221 is a deficient number, since it is larger than the sum of its proper divisors (7028259).

21016221 is a wasteful number, since it uses less digits than its factorization.

21016221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5715.

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 21016221 is about 4584.3452095147. The cubic root of 21016221 is about 275.9634350846.

Adding to 21016221 its reverse (12261012), we get a palindrome (33277233).

The spelling of 21016221 in words is "twenty-one million, sixteen thousand, two hundred twenty-one".