216555640 has 64 divisors (see below), whose sum is σ = 560064960. Its totient is φ = 73820160.

The previous prime is 216555637. The next prime is 216555643. The reversal of 216555640 is 46555612.

It is an interprime number because it is at equal distance from previous prime (216555637) and next prime (216555643).

It is a junction number, because it is equal to n+sod(n) for n = 216555596 and 216555605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216555643) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48544 + ... + 52816.

It is an arithmetic number, because the mean of its divisors is an integer number (8751015).

Almost surely, 2^216555640 is an apocalyptic number.

216555640 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 216555640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (280032480).

216555640 is an abundant number, since it is smaller than the sum of its proper divisors (343509320).

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

216555640 is a wasteful number, since it uses less digits than its factorization.

216555640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4472 (or 4468 counting only the distinct ones).

The product of its (nonzero) digits is 36000, while the sum is 34.

The square root of 216555640 is about 14715.8295722667. The cubic root of 216555640 is about 600.5140409589.

The spelling of 216555640 in words is "two hundred sixteen million, five hundred fifty-five thousand, six hundred forty".