21187138 has 8 divisors (see below), whose sum is σ = 36320832. Its totient is φ = 9080196.

The previous prime is 21187129. The next prime is 21187189. The reversal of 21187138 is 83178112.

It is a happy number.

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 756670 + ... + 756697.

It is an arithmetic number, because the mean of its divisors is an integer number (4540104).

Almost surely, 2^21187138 is an apocalyptic number.

21187138 is a deficient number, since it is larger than the sum of its proper divisors (15133694).

21187138 is a wasteful number, since it uses less digits than its factorization.

21187138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1513376.

The product of its digits is 2688, while the sum is 31.

The square root of 21187138 is about 4602.9488374302. The cubic root of 21187138 is about 276.7095183702.

The spelling of 21187138 in words is "twenty-one million, one hundred eighty-seven thousand, one hundred thirty-eight".