21718017 has 8 divisors (see below), whose sum is σ = 32174880. Its totient is φ = 14478660.

The previous prime is 21717989. The next prime is 21718033. The reversal of 21718017 is 71081712.

It is not a de Polignac number, because 21718017 - 2⁶ = 21717953 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 804371 = 21718017 / (2 + 1 + 7 + 1 + 8 + 0 + 1 + 7).

It is not an unprimeable number, because it can be changed into a prime (21718087) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 402159 + ... + 402212.

It is an arithmetic number, because the mean of its divisors is an integer number (4021860).

Almost surely, 2^21718017 is an apocalyptic number.

21718017 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21718017 is a deficient number, since it is larger than the sum of its proper divisors (10456863).

21718017 is an equidigital number, since it uses as much as digits as its factorization.

21718017 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 804380 (or 804374 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 27.

The square root of 21718017 is about 4660.2593275482. The cubic root of 21718017 is about 279.0016186748.

Adding to 21718017 its reverse (71081712), we get a palindrome (92799729).

The spelling of 21718017 in words is "twenty-one million, seven hundred eighteen thousand, seventeen".