21002221 has 8 divisors (see below), whose sum is σ = 21765888. Its totient is φ = 20244000.

The previous prime is 21002213. The next prime is 21002231. The reversal of 21002221 is 12220012.

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

It is a cyclic number.

It is not a de Polignac number, because 21002221 - 2³ = 21002213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21002198 and 21002207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002231) 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, 7506 + ... + 9916.

It is an arithmetic number, because the mean of its divisors is an integer number (2720736).

Almost surely, 2^21002221 is an apocalyptic number.

It is an amenable number.

21002221 is a deficient number, since it is larger than the sum of its proper divisors (763667).

21002221 is a wasteful number, since it uses less digits than its factorization.

21002221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2723.

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21002221 is about 4582.8180195159. The cubic root of 21002221 is about 275.9021435978.

Adding to 21002221 its reverse (12220012), we get a palindrome (33222233).

The spelling of 21002221 in words is "twenty-one million, two thousand, two hundred twenty-one".