216645840 has 200 divisors, whose sum is σ = 765204000. Its totient is φ = 56795904.

The previous prime is 216645833. The next prime is 216645857. The reversal of 216645840 is 48546612.

216645840 is a `hidden beast` number, since 2 + 1 + 6 + 645 + 8 + 4 + 0 = 666.

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 = 216645795 and 216645804.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 433911 + ... + 434409.

It is an arithmetic number, because the mean of its divisors is an integer number (3826020).

Almost surely, 2^216645840 is an apocalyptic number.

216645840 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 216645840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (382602000).

216645840 is an abundant number, since it is smaller than the sum of its proper divisors (548558160).

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

216645840 is a wasteful number, since it uses less digits than its factorization.

216645840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 591 (or 576 counting only the distinct ones).

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

The square root of 216645840 is about 14718.8939801875. The cubic root of 216645840 is about 600.5974049814.

The spelling of 216645840 in words is "two hundred sixteen million, six hundred forty-five thousand, eight hundred forty".