215864640 has 168 divisors, whose sum is σ = 786338280. Its totient is φ = 54165504.

The previous prime is 215864611. The next prime is 215864659. The reversal of 215864640 is 46468512.

215864640 is a `hidden beast` number, since 2 + 1 + 5 + 8 + 6 + 4 + 640 = 666.

215864640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 9884736 + 205979904 = 3144^2 + 14352^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 215864595 and 215864604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 46756 + ... + 51164.

It is an arithmetic number, because the mean of its divisors is an integer number (4680585).

Almost surely, 2^215864640 is an apocalyptic number.

215864640 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 215864640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (393169140).

215864640 is an abundant number, since it is smaller than the sum of its proper divisors (570473640).

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

215864640 is a wasteful number, since it uses less digits than its factorization.

215864640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4449 (or 4436 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 36.

The square root of 215864640 is about 14692.3326943001. The cubic root of 215864640 is about 599.8746404768.

The spelling of 215864640 in words is "two hundred fifteen million, eight hundred sixty-four thousand, six hundred forty".