21571217 has 8 divisors (see below), whose sum is σ = 22576320. Its totient is φ = 20571760.

The previous prime is 21571169. The next prime is 21571229. The reversal of 21571217 is 71217512.

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 21571217 - 2⁶ = 21571153 is a prime.

It is a super-2 number, since 2×21571217² = 930634805722178, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21571237) 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, 7742 + ... + 10152.

It is an arithmetic number, because the mean of its divisors is an integer number (2822040).

Almost surely, 2^21571217 is an apocalyptic number.

It is an amenable number.

21571217 is a deficient number, since it is larger than the sum of its proper divisors (1005103).

21571217 is a wasteful number, since it uses less digits than its factorization.

21571217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2823.

The product of its digits is 980, while the sum is 26.

The square root of 21571217 is about 4644.4824254162. The cubic root of 21571217 is about 278.3715723894.

Adding to 21571217 its reverse (71217512), we get a palindrome (92788729).

The spelling of 21571217 in words is "twenty-one million, five hundred seventy-one thousand, two hundred seventeen".