21718417 has 16 divisors (see below), whose sum is σ = 26438400. Its totient is φ = 17799936.

The previous prime is 21718409. The next prime is 21718421. The reversal of 21718417 is 71481712.

It is not a de Polignac number, because 21718417 - 2³ = 21718409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21718427) 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, 6513 + ... + 9265.

It is an arithmetic number, because the mean of its divisors is an integer number (1652400).

Almost surely, 2^21718417 is an apocalyptic number.

It is an amenable number.

21718417 is a deficient number, since it is larger than the sum of its proper divisors (4719983).

21718417 is an equidigital number, since it uses as much as digits as its factorization.

21718417 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2797 (or 2783 counting only the distinct ones).

The product of its digits is 3136, while the sum is 31.

The square root of 21718417 is about 4660.3022434173. The cubic root of 21718417 is about 279.0033315378.

The spelling of 21718417 in words is "twenty-one million, seven hundred eighteen thousand, four hundred seventeen".