21128187 has 8 divisors (see below), whose sum is σ = 28192320. Its totient is φ = 14074760.

The previous prime is 21128183. The next prime is 21128189. The reversal of 21128187 is 78182112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21128187 - 2² = 21128183 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21128183) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5512 + ... + 8522.

It is an arithmetic number, because the mean of its divisors is an integer number (3524040).

Almost surely, 2^21128187 is an apocalyptic number.

21128187 is a deficient number, since it is larger than the sum of its proper divisors (7064133).

21128187 is a wasteful number, since it uses less digits than its factorization.

21128187 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5353.

The product of its digits is 1792, while the sum is 30.

The square root of 21128187 is about 4596.5407645315. The cubic root of 21128187 is about 276.4526415276.

The spelling of 21128187 in words is "twenty-one million, one hundred twenty-eight thousand, one hundred eighty-seven".