216561380 has 72 divisors (see below), whose sum is σ = 533220408. Its totient is φ = 73661952.

The previous prime is 216561379. The next prime is 216561391. The reversal of 216561380 is 83165612.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 37429924 + 179131456 = 6118^2 + 13384^2 .

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, 133454 + ... + 135066.

It is an arithmetic number, because the mean of its divisors is an integer number (7405839).

Almost surely, 2^216561380 is an apocalyptic number.

216561380 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 216561380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (266610204).

216561380 is an abundant number, since it is smaller than the sum of its proper divisors (316659028).

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

216561380 is a wasteful number, since it uses less digits than its factorization.

216561380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1773 (or 1764 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 32.

The square root of 216561380 is about 14716.0245990553. The cubic root of 216561380 is about 600.5193466317.

The spelling of 216561380 in words is "two hundred sixteen million, five hundred sixty-one thousand, three hundred eighty".