21078187 has 12 divisors (see below), whose sum is σ = 22978944. Its totient is φ = 19325280.

The previous prime is 21078179. The next prime is 21078191. The reversal of 21078187 is 78187012.

It is not a de Polignac number, because 21078187 - 2³ = 21078179 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21078587) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31953 + ... + 32605.

It is an arithmetic number, because the mean of its divisors is an integer number (1914912).

Almost surely, 2^21078187 is an apocalyptic number.

21078187 is a deficient number, since it is larger than the sum of its proper divisors (1900757).

21078187 is a wasteful number, since it uses less digits than its factorization.

21078187 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 870 (or 857 counting only the distinct ones).

The product of its (nonzero) digits is 6272, while the sum is 34.

The square root of 21078187 is about 4591.0986702531. The cubic root of 21078187 is about 276.2343935820.

The spelling of 21078187 in words is "twenty-one million, seventy-eight thousand, one hundred eighty-seven".