21500640 has 288 divisors, whose sum is σ = 88058880. Its totient is φ = 4852224.

The previous prime is 21500627. The next prime is 21500641. The reversal of 21500640 is 4600512.

It is a happy number.

21500640 is a `hidden beast` number, since 21 + 5 + 0 + 0 + 640 = 666.

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 (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21500641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 272121 + ... + 272199.

It is an arithmetic number, because the mean of its divisors is an integer number (305760).

Almost surely, 2^21500640 is an apocalyptic number.

21500640 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 21500640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44029440).

21500640 is an abundant number, since it is smaller than the sum of its proper divisors (66558240).

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

21500640 is an equidigital number, since it uses as much as digits as its factorization.

21500640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116 (or 96 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21500640 is about 4636.8782602091. The cubic root of 21500640 is about 278.0676473922.

The spelling of 21500640 in words is "twenty-one million, five hundred thousand, six hundred forty".