21218201 has 4 divisors (see below), whose sum is σ = 21380304. Its totient is φ = 21056100.

The previous prime is 21218191. The next prime is 21218233. The reversal of 21218201 is 10281212.

It is a happy number.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21218201 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 21218201.

It is not an unprimeable number, because it can be changed into a prime (21218251) 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, 80855 + ... + 81116.

It is an arithmetic number, because the mean of its divisors is an integer number (5345076).

Almost surely, 2^21218201 is an apocalyptic number.

It is an amenable number.

21218201 is a deficient number, since it is larger than the sum of its proper divisors (162103).

21218201 is a wasteful number, since it uses less digits than its factorization.

21218201 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162102.

The product of its (nonzero) digits is 64, while the sum is 17.

The square root of 21218201 is about 4606.3218515427. The cubic root of 21218201 is about 276.8446826151.

Adding to 21218201 its reverse (10281212), we get a palindrome (31499413).

The spelling of 21218201 in words is "twenty-one million, two hundred eighteen thousand, two hundred one".