215781540 has 96 divisors (see below), whose sum is σ = 660535680. Its totient is φ = 52310016.

The previous prime is 215781529. The next prime is 215781541. The reversal of 215781540 is 45187512.

It is not an unprimeable number, because it can be changed into a prime (215781541) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 50196 + ... + 54324.

It is an arithmetic number, because the mean of its divisors is an integer number (6880580).

Almost surely, 2^215781540 is an apocalyptic number.

215781540 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 215781540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (330267840).

215781540 is an abundant number, since it is smaller than the sum of its proper divisors (444754140).

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

215781540 is a wasteful number, since it uses less digits than its factorization.

215781540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4221 (or 4219 counting only the distinct ones).

The product of its (nonzero) digits is 11200, while the sum is 33.

The square root of 215781540 is about 14689.5044164192. The cubic root of 215781540 is about 599.7976539900.

The spelling of 215781540 in words is "two hundred fifteen million, seven hundred eighty-one thousand, five hundred forty".