21378285 has 12 divisors (see below), whose sum is σ = 37055772. Its totient is φ = 11401728.

The previous prime is 21378281. The next prime is 21378289. The reversal of 21378285 is 58287312.

21378285 is a `hidden beast` number, since 2 + 1 + 378 + 285 = 666.

It is an interprime number because it is at equal distance from previous prime (21378281) and next prime (21378289).

It can be written as a sum of positive squares in 2 ways, for example, as 6215049 + 15163236 = 2493^2 + 3894^2 .

It is not a de Polignac number, because 21378285 - 2² = 21378281 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378281) 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 11 ways as a sum of consecutive naturals, for example, 237492 + ... + 237581.

It is an arithmetic number, because the mean of its divisors is an integer number (3087981).

Almost surely, 2^21378285 is an apocalyptic number.

It is an amenable number.

21378285 is a deficient number, since it is larger than the sum of its proper divisors (15677487).

21378285 is a wasteful number, since it uses less digits than its factorization.

21378285 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 475084 (or 475081 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 21378285 is about 4623.6657534904. The cubic root of 21378285 is about 277.5391714852.

The spelling of 21378285 in words is "twenty-one million, three hundred seventy-eight thousand, two hundred eighty-five".