21387111 has 4 divisors (see below), whose sum is σ = 28516152. Its totient is φ = 14258072.

The previous prime is 21387109. The next prime is 21387151. The reversal of 21387111 is 11178312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21387111 - 2¹ = 21387109 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3564516 + ... + 3564521.

It is an arithmetic number, because the mean of its divisors is an integer number (7129038).

Almost surely, 2^21387111 is an apocalyptic number.

21387111 is a deficient number, since it is larger than the sum of its proper divisors (7129041).

21387111 is an equidigital number, since it uses as much as digits as its factorization.

21387111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7129040.

The product of its digits is 336, while the sum is 24.

The square root of 21387111 is about 4624.6200925049. The cubic root of 21387111 is about 277.5773601379.

The spelling of 21387111 in words is "twenty-one million, three hundred eighty-seven thousand, one hundred eleven".