21620171 has 4 divisors (see below), whose sum is σ = 21646200. Its totient is φ = 21594144.

The previous prime is 21620153. The next prime is 21620189. The reversal of 21620171 is 17102612.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21620153) and next prime (21620189).

It is a cyclic number.

It is not a de Polignac number, because 21620171 - 2¹⁸ = 21358027 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21620101) 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, 11726 + ... + 13443.

It is an arithmetic number, because the mean of its divisors is an integer number (5411550).

Almost surely, 2^21620171 is an apocalyptic number.

21620171 is a deficient number, since it is larger than the sum of its proper divisors (26029).

21620171 is an equidigital number, since it uses as much as digits as its factorization.

21620171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26028.

The product of its (nonzero) digits is 168, while the sum is 20.

The square root of 21620171 is about 4649.7495631485. The cubic root of 21620171 is about 278.5819933127.

Adding to 21620171 its reverse (17102612), we get a palindrome (38722783).

The spelling of 21620171 in words is "twenty-one million, six hundred twenty thousand, one hundred seventy-one".