21867 has 8 divisors (see below), whose sum is σ = 30096. Its totient is φ = 14112.

The previous prime is 21863. The next prime is 21871. The reversal of 21867 is 76812.

It is an interprime number because it is at equal distance from previous prime (21863) and next prime (21871).

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

It is not a de Polignac number, because 21867 - 2² = 21863 is a prime.

21867 is an undulating number in base 14.

21867 is a lucky number.

It is a plaindrome in base 4 and base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21863) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13 + ... + 209.

It is an arithmetic number, because the mean of its divisors is an integer number (3762).

2²¹⁸⁶⁷ is an apocalyptic number.

21867 is a deficient number, since it is larger than the sum of its proper divisors (8229).

21867 is a wasteful number, since it uses less digits than its factorization.

21867 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 237.

The product of its digits is 672, while the sum is 24.

The square root of 21867 is about 147.8749471682. The cubic root of 21867 is about 27.9638137986.

Subtracting 21867 from its reverse (76812), we obtain a palindrome (54945).

It can be divided in two parts, 21 and 867, that added together give a palindrome (888).

The spelling of 21867 in words is "twenty-one thousand, eight hundred sixty-seven".