215685640 has 16 divisors (see below), whose sum is σ = 485292780. Its totient is φ = 86274240.

The previous prime is 215685637. The next prime is 215685641. The reversal of 215685640 is 46586512.

It can be written as a sum of positive squares in 2 ways, for example, as 179613604 + 36072036 = 13402^2 + 6006^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 215685640.

It is not an unprimeable number, because it can be changed into a prime (215685641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2696031 + ... + 2696110.

Almost surely, 2^215685640 is an apocalyptic number.

215685640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

215685640 is an abundant number, since it is smaller than the sum of its proper divisors (269607140).

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

215685640 is a wasteful number, since it uses less digits than its factorization.

215685640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5392152 (or 5392148 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 37.

The square root of 215685640 is about 14686.2398182789. The cubic root of 215685640 is about 599.7087846048.

The spelling of 215685640 in words is "two hundred fifteen million, six hundred eighty-five thousand, six hundred forty".