21718385 has 16 divisors (see below), whose sum is σ = 28491456. Its totient is φ = 15795648.

The previous prime is 21718381. The next prime is 21718391. The reversal of 21718385 is 58381712.

It is a cyclic number.

It is not a de Polignac number, because 21718385 - 2² = 21718381 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21718381) 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, 1862 + ... + 6848.

It is an arithmetic number, because the mean of its divisors is an integer number (1780716).

Almost surely, 2^21718385 is an apocalyptic number.

It is an amenable number.

21718385 is a deficient number, since it is larger than the sum of its proper divisors (6773071).

21718385 is a wasteful number, since it uses less digits than its factorization.

21718385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5072.

The product of its digits is 13440, while the sum is 35.

The square root of 21718385 is about 4660.2988101623. The cubic root of 21718385 is about 279.0031945096.

The spelling of 21718385 in words is "twenty-one million, seven hundred eighteen thousand, three hundred eighty-five".