21201217 has 4 divisors (see below), whose sum is σ = 21285936. Its totient is φ = 21116500.

The previous prime is 21201209. The next prime is 21201251. The reversal of 21201217 is 71210212.

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 not a de Polignac number, because 21201217 - 2³ = 21201209 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 21201217.

It is not an unprimeable number, because it can be changed into a prime (21201287) 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, 41983 + ... + 42484.

It is an arithmetic number, because the mean of its divisors is an integer number (5321484).

Almost surely, 2^21201217 is an apocalyptic number.

It is an amenable number.

21201217 is a deficient number, since it is larger than the sum of its proper divisors (84719).

21201217 is an equidigital number, since it uses as much as digits as its factorization.

21201217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84718.

The product of its (nonzero) digits is 56, while the sum is 16.

The square root of 21201217 is about 4604.4779291468. The cubic root of 21201217 is about 276.7707965963.

Adding to 21201217 its reverse (71210212), we get a palindrome (92411429).

The spelling of 21201217 in words is "twenty-one million, two hundred one thousand, two hundred seventeen".