21279379 has 4 divisors (see below), whose sum is σ = 23213880. Its totient is φ = 19344880.

The previous prime is 21279331. The next prime is 21279383. The reversal of 21279379 is 97397212.

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 21279379 - 2¹⁵ = 21246611 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 Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21279319) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 967234 + ... + 967255.

It is an arithmetic number, because the mean of its divisors is an integer number (5803470).

Almost surely, 2^21279379 is an apocalyptic number.

21279379 is a deficient number, since it is larger than the sum of its proper divisors (1934501).

21279379 is a wasteful number, since it uses less digits than its factorization.

21279379 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1934500.

The product of its digits is 47628, while the sum is 40.

The square root of 21279379 is about 4612.9577279659. The cubic root of 21279379 is about 277.1105008180.

The spelling of 21279379 in words is "twenty-one million, two hundred seventy-nine thousand, three hundred seventy-nine".