21417021 has 16 divisors (see below), whose sum is σ = 31902720. Its totient is φ = 14199840.

The previous prime is 21416999. The next prime is 21417023. The reversal of 21417021 is 12071412.

It is not a de Polignac number, because 21417021 - 2¹¹ = 21414973 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21416985 and 21417003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21417023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3081 + ... + 7233.

It is an arithmetic number, because the mean of its divisors is an integer number (1993920).

Almost surely, 2^21417021 is an apocalyptic number.

It is an amenable number.

21417021 is a deficient number, since it is larger than the sum of its proper divisors (10485699).

21417021 is a wasteful number, since it uses less digits than its factorization.

21417021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4353 (or 4347 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 21417021 is about 4627.8527418231. The cubic root of 21417021 is about 277.7066977182.

Adding to 21417021 its reverse (12071412), we get a palindrome (33488433).

The spelling of 21417021 in words is "twenty-one million, four hundred seventeen thousand, twenty-one".