21738240 has 288 divisors, whose sum is σ = 83885760. Its totient is φ = 5308416.

The previous prime is 21738239. The next prime is 21738247. The reversal of 21738240 is 4283712.

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21738247) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 587502 + ... + 587538.

It is an arithmetic number, because the mean of its divisors is an integer number (291270).

Almost surely, 2^21738240 is an apocalyptic number.

21738240 is a gapful number since it is divisible by the number (20) 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 21738240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41942880).

21738240 is an abundant number, since it is smaller than the sum of its proper divisors (62147520).

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

21738240 is a wasteful number, since it uses less digits than its factorization.

21738240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84 (or 64 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21738240 is about 4662.4285517314. The cubic root of 21738240 is about 279.0881904117.

The spelling of 21738240 in words is "twenty-one million, seven hundred thirty-eight thousand, two hundred forty".