215663440 has 20 divisors (see below), whose sum is σ = 501417684. Its totient is φ = 86265344.

The previous prime is 215663431. The next prime is 215663449. The reversal of 215663440 is 44366512.

It is an interprime number because it is at equal distance from previous prime (215663431) and next prime (215663449).

It can be written as a sum of positive squares in 2 ways, for example, as 112275216 + 103388224 = 10596^2 + 10168^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215663449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1347817 + ... + 1347976.

Almost surely, 2^215663440 is an apocalyptic number.

215663440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

215663440 is an abundant number, since it is smaller than the sum of its proper divisors (285754244).

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

215663440 is a wasteful number, since it uses less digits than its factorization.

215663440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2695806 (or 2695800 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 31.

The square root of 215663440 is about 14685.4839893005. The cubic root of 215663440 is about 599.6882083751.

The spelling of 215663440 in words is "two hundred fifteen million, six hundred sixty-three thousand, four hundred forty".