21867391 has 16 divisors (see below), whose sum is σ = 27574848. Its totient is φ = 16876800.

The previous prime is 21867383. The next prime is 21867401. The reversal of 21867391 is 19376812.

It is a cyclic number.

It is not a de Polignac number, because 21867391 - 2³ = 21867383 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21867391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21867331) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 801 + ... + 6661.

It is an arithmetic number, because the mean of its divisors is an integer number (1723428).

Almost surely, 2^21867391 is an apocalyptic number.

21867391 is a deficient number, since it is larger than the sum of its proper divisors (5707457).

21867391 is a wasteful number, since it uses less digits than its factorization.

21867391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5922.

The product of its digits is 18144, while the sum is 37.

The square root of 21867391 is about 4676.2582264028. The cubic root of 21867391 is about 279.6398046963.

The spelling of 21867391 in words is "twenty-one million, eight hundred sixty-seven thousand, three hundred ninety-one".