215820 has 72 divisors (see below), whose sum is σ = 720720. Its totient is φ = 51840.

The previous prime is 215801. The next prime is 215827. The reversal of 215820 is 28512.

215820 = T₁ + T₂ + ... + T₁₀₈.

215820 is a nontrivial binomial coefficient, being equal to C(110, 3).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 215793 and 215802.

It is not an unprimeable number, because it can be changed into a prime (215827) by changing a digit.

It is the 108-th tetrahedral number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1926 + ... + 2034.

It is an arithmetic number, because the mean of its divisors is an integer number (10010).

2²¹⁵⁸²⁰ is an apocalyptic number.

215820 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 215820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (360360).

215820 is an abundant number, since it is smaller than the sum of its proper divisors (504900).

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

215820 is a wasteful number, since it uses less digits than its factorization.

215820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 215820 is about 464.5643120172. The cubic root of 215820 is about 59.9833287016.

It can be divided in two parts, 215 and 820, that added together give a triangular number (1035 = T₄₅).

The spelling of 215820 in words is "two hundred fifteen thousand, eight hundred twenty".