215640 has 48 divisors (see below), whose sum is σ = 702000. Its totient is φ = 57408.

The previous prime is 215617. The next prime is 215653. The reversal of 215640 is 46512.

215640 = T₆₁ + T₆₂ + ... + T₁₁₄.

215640 = 7² + 8² + ... + 86².

It is a happy number.

215640 is a `hidden beast` number, since 21 + 5 + 640 = 666.

215640 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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

It is a congruent number.

It is an unprimeable number.

215640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 61 + ... + 659.

It is an arithmetic number, because the mean of its divisors is an integer number (14625).

2²¹⁵⁶⁴⁰ is an apocalyptic number.

215640 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 215640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (351000).

215640 is an abundant number, since it is smaller than the sum of its proper divisors (486360).

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

215640 is a wasteful number, since it uses less digits than its factorization.

215640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 616 (or 609 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 215640 is about 464.3705417013. The cubic root of 215640 is about 59.9666481310.

The spelling of 215640 in words is "two hundred fifteen thousand, six hundred forty".