21018417 has 16 divisors (see below), whose sum is σ = 33133440. Its totient is φ = 11596032.

The previous prime is 21018407. The next prime is 21018461. The reversal of 21018417 is 71481012.

It is not a de Polignac number, because 21018417 - 2⁴ = 21018401 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21018407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16648 + ... + 17865.

It is an arithmetic number, because the mean of its divisors is an integer number (2070840).

Almost surely, 2^21018417 is an apocalyptic number.

It is an amenable number.

21018417 is a deficient number, since it is larger than the sum of its proper divisors (12115023).

21018417 is a wasteful number, since it uses less digits than its factorization.

21018417 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34552.

The product of its (nonzero) digits is 448, while the sum is 24.

The square root of 21018417 is about 4584.5847140172. The cubic root of 21018417 is about 275.9730466223.

Adding to 21018417 its reverse (71481012), we get a palindrome (92499429).

The spelling of 21018417 in words is "twenty-one million, eighteen thousand, four hundred seventeen".