21138887 has 16 divisors (see below), whose sum is σ = 27744000. Its totient is φ = 15603840.

The previous prime is 21138881. The next prime is 21138911. The reversal of 21138887 is 78883112.

It is not a de Polignac number, because 21138887 - 2⁶ = 21138823 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21138887.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138881) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5762 + ... + 8687.

It is an arithmetic number, because the mean of its divisors is an integer number (1734000).

Almost surely, 2^21138887 is an apocalyptic number.

21138887 is a deficient number, since it is larger than the sum of its proper divisors (6605113).

21138887 is a wasteful number, since it uses less digits than its factorization.

21138887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14486.

The product of its digits is 21504, while the sum is 38.

The square root of 21138887 is about 4597.7045359614. The cubic root of 21138887 is about 276.4993018500.

The spelling of 21138887 in words is "twenty-one million, one hundred thirty-eight thousand, eight hundred eighty-seven".