21879121 has 8 divisors (see below), whose sum is σ = 23909184. Its totient is φ = 19855920.

The previous prime is 21879103. The next prime is 21879139. The reversal of 21879121 is 12197812.

It is an interprime number because it is at equal distance from previous prime (21879103) and next prime (21879139).

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

It is a cyclic number.

It is not a de Polignac number, because 21879121 - 2¹¹ = 21877073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21879101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6835 + ... + 9511.

It is an arithmetic number, because the mean of its divisors is an integer number (2988648).

Almost surely, 2^21879121 is an apocalyptic number.

It is an amenable number.

21879121 is a deficient number, since it is larger than the sum of its proper divisors (2030063).

21879121 is a wasteful number, since it uses less digits than its factorization.

21879121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3431.

The product of its digits is 2016, while the sum is 31.

The square root of 21879121 is about 4677.5122661517. The cubic root of 21879121 is about 279.6897967686.

It can be divided in two parts, 218791 and 21, that added together give a palindrome (218812).

The spelling of 21879121 in words is "twenty-one million, eight hundred seventy-nine thousand, one hundred twenty-one".