21271217 has 4 divisors (see below), whose sum is σ = 23204976. Its totient is φ = 19337460.

The previous prime is 21271207. The next prime is 21271223. The reversal of 21271217 is 71217212.

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 21271217 - 2⁶ = 21271153 is a prime.

It is a super-2 number, since 2×21271217² = 904929345322178, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21271192 and 21271201.

It is not an unprimeable number, because it can be changed into a prime (21271207) 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, 966863 + ... + 966884.

It is an arithmetic number, because the mean of its divisors is an integer number (5801244).

Almost surely, 2^21271217 is an apocalyptic number.

It is an amenable number.

21271217 is a deficient number, since it is larger than the sum of its proper divisors (1933759).

21271217 is a wasteful number, since it uses less digits than its factorization.

21271217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1933758.

The product of its digits is 392, while the sum is 23.

The square root of 21271217 is about 4612.0729612616. The cubic root of 21271217 is about 277.0750664326.

Adding to 21271217 its reverse (71217212), we get a palindrome (92488429).

The spelling of 21271217 in words is "twenty-one million, two hundred seventy-one thousand, two hundred seventeen".