21711217 has 4 divisors (see below), whose sum is σ = 23684976. Its totient is φ = 19737460.

The previous prime is 21711163. The next prime is 21711229. The reversal of 21711217 is 71211712.

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 21711217 - 2¹⁹ = 21186929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21711317) 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, 986863 + ... + 986884.

It is an arithmetic number, because the mean of its divisors is an integer number (5921244).

Almost surely, 2^21711217 is an apocalyptic number.

It is an amenable number.

21711217 is a deficient number, since it is larger than the sum of its proper divisors (1973759).

21711217 is a wasteful number, since it uses less digits than its factorization.

21711217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1973758.

The product of its digits is 196, while the sum is 22.

The square root of 21711217 is about 4659.5296972978. The cubic root of 21711217 is about 278.9724967857.

Multiplying 21711217 by its sum of digits (22), we get a palindrome (477646774).

Adding to 21711217 its reverse (71211712), we get a palindrome (92922929).

The spelling of 21711217 in words is "twenty-one million, seven hundred eleven thousand, two hundred seventeen".