21879427 has 4 divisors (see below), whose sum is σ = 22633920. Its totient is φ = 21124936.

The previous prime is 21879379. The next prime is 21879443. The reversal of 21879427 is 72497812.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21879427 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21879427.

It is not an unprimeable number, because it can be changed into a prime (21879457) 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 3 ways as a sum of consecutive naturals, for example, 377203 + ... + 377260.

It is an arithmetic number, because the mean of its divisors is an integer number (5658480).

Almost surely, 2^21879427 is an apocalyptic number.

21879427 is a deficient number, since it is larger than the sum of its proper divisors (754493).

21879427 is an equidigital number, since it uses as much as digits as its factorization.

21879427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 754492.

The product of its digits is 56448, while the sum is 40.

The square root of 21879427 is about 4677.5449757325. The cubic root of 21879427 is about 279.6911006704.

The spelling of 21879427 in words is "twenty-one million, eight hundred seventy-nine thousand, four hundred twenty-seven".