21979205 has 8 divisors (see below), whose sum is σ = 26736792. Its totient is φ = 17342208.

The previous prime is 21979189. The next prime is 21979213. The reversal of 21979205 is 50297912.

It can be written as a sum of positive squares in 4 ways, for example, as 11236 + 21967969 = 106^2 + 4687^2 .

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 21979205 - 2⁴ = 21979189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 29744 + ... + 30473.

It is an arithmetic number, because the mean of its divisors is an integer number (3342099).

Almost surely, 2^21979205 is an apocalyptic number.

It is an amenable number.

21979205 is a deficient number, since it is larger than the sum of its proper divisors (4757587).

21979205 is an equidigital number, since it uses as much as digits as its factorization.

21979205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60295.

The product of its (nonzero) digits is 11340, while the sum is 35.

The square root of 21979205 is about 4688.1984812932. The cubic root of 21979205 is about 280.1156197678.

The spelling of 21979205 in words is "twenty-one million, nine hundred seventy-nine thousand, two hundred five".