21252217 has 16 divisors (see below), whose sum is σ = 25069824. Its totient is φ = 17640000.

The previous prime is 21252211. The next prime is 21252223. The reversal of 21252217 is 71225212.

It is an interprime number because it is at equal distance from previous prime (21252211) and next prime (21252223).

It is not a de Polignac number, because 21252217 - 2¹⁵ = 21219449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21252211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29967 + ... + 30667.

It is an arithmetic number, because the mean of its divisors is an integer number (1566864).

Almost surely, 2^21252217 is an apocalyptic number.

It is an amenable number.

21252217 is a deficient number, since it is larger than the sum of its proper divisors (3817607).

21252217 is an equidigital number, since it uses as much as digits as its factorization.

21252217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 840.

The product of its digits is 560, while the sum is 22.

The square root of 21252217 is about 4610.0126897873. The cubic root of 21252217 is about 276.9925449909.

Adding to 21252217 its reverse (71225212), we get a palindrome (92477429).

The spelling of 21252217 in words is "twenty-one million, two hundred fifty-two thousand, two hundred seventeen".