21718368 has 252 divisors, whose sum is σ = 78499260. Its totient is φ = 5878656.

The previous prime is 21718363. The next prime is 21718369. The reversal of 21718368 is 86381712.

It is a tau number, because it is divible by the number of its divisors (252).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21718363) 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 41 ways as a sum of consecutive naturals, for example, 1143063 + ... + 1143081.

It is an arithmetic number, because the mean of its divisors is an integer number (311505).

Almost surely, 2^21718368 is an apocalyptic number.

21718368 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21718368, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39249630).

21718368 is an abundant number, since it is smaller than the sum of its proper divisors (56780892).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21718368 is an equidigital number, since it uses as much as digits as its factorization.

21718368 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61 (or 31 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 21718368 is about 4660.2969862445. The cubic root of 21718368 is about 279.0031217133.

The spelling of 21718368 in words is "twenty-one million, seven hundred eighteen thousand, three hundred sixty-eight".