21687120 has 240 divisors, whose sum is σ = 89910912. Its totient is φ = 4561920.

The previous prime is 21687119. The next prime is 21687191. The reversal of 21687120 is 2178612.

It is a tau number, because it is divible by the number of its divisors (240).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 65355 + ... + 65685.

Almost surely, 2^21687120 is an apocalyptic number.

21687120 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 21687120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44955456).

21687120 is an abundant number, since it is smaller than the sum of its proper divisors (68223792).

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

21687120 is a wasteful number, since it uses less digits than its factorization.

21687120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 370 (or 361 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21687120 is about 4656.9432034329. The cubic root of 21687120 is about 278.8692492520.

The spelling of 21687120 in words is "twenty-one million, six hundred eighty-seven thousand, one hundred twenty".