21718140 has 48 divisors (see below), whose sum is σ = 64014720. Its totient is φ = 5486400.

The previous prime is 21718133. The next prime is 21718189. The reversal of 21718140 is 4181712.

It is a self number, because there is not a number n which added to its sum of digits gives 21718140.

It is a congruent number.

It is an unprimeable number.

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, 8386 + ... + 10665.

It is an arithmetic number, because the mean of its divisors is an integer number (1333640).

Almost surely, 2^21718140 is an apocalyptic number.

21718140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21718140 is an abundant number, since it is smaller than the sum of its proper divisors (42296580).

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

21718140 is a wasteful number, since it uses less digits than its factorization.

21718140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19082 (or 19080 counting only the distinct ones).

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

The square root of 21718140 is about 4660.2725242200. The cubic root of 21718140 is about 279.0021453825.

Adding to 21718140 its reverse (4181712), we get a palindrome (25899852).

The spelling of 21718140 in words is "twenty-one million, seven hundred eighteen thousand, one hundred forty".