21387138 has 16 divisors (see below), whose sum is σ = 42853536. Its totient is φ = 7115840.

The previous prime is 21387109. The next prime is 21387151. The reversal of 21387138 is 83178312.

It is a junction number, because it is equal to n+sod(n) for n = 21387099 and 21387108.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 553 + ... + 6563.

It is an arithmetic number, because the mean of its divisors is an integer number (2678346).

Almost surely, 2^21387138 is an apocalyptic number.

21387138 is an abundant number, since it is smaller than the sum of its proper divisors (21466398).

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

21387138 is a wasteful number, since it uses less digits than its factorization.

21387138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6609.

The product of its digits is 8064, while the sum is 33.

The square root of 21387138 is about 4624.6230116627. The cubic root of 21387138 is about 277.5774769464.

The spelling of 21387138 in words is "twenty-one million, three hundred eighty-seven thousand, one hundred thirty-eight".