21879079 has 4 divisors (see below), whose sum is σ = 22633560. Its totient is φ = 21124600.

The previous prime is 21879047. The next prime is 21879083. The reversal of 21879079 is 97097812.

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 21879079 - 2⁵ = 21879047 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21879019) 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, 377197 + ... + 377254.

It is an arithmetic number, because the mean of its divisors is an integer number (5658390).

Almost surely, 2^21879079 is an apocalyptic number.

21879079 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21879079 is a deficient number, since it is larger than the sum of its proper divisors (754481).

21879079 is an equidigital number, since it uses as much as digits as its factorization.

21879079 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 754480.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 21879079 is about 4677.5077765836. The cubic root of 21879079 is about 279.6896178007.

It can be divided in two parts, 218 and 79079, that added together give a palindrome (79297).

The spelling of 21879079 in words is "twenty-one million, eight hundred seventy-nine thousand, seventy-nine".