21165979 has 4 divisors (see below), whose sum is σ = 21215520. Its totient is φ = 21116440.

The previous prime is 21165973. The next prime is 21165997. The reversal of 21165979 is 97956112.

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 21165979 - 2³ = 21165971 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21165971) 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, 24124 + ... + 24985.

It is an arithmetic number, because the mean of its divisors is an integer number (5303880).

Almost surely, 2^21165979 is an apocalyptic number.

21165979 is a deficient number, since it is larger than the sum of its proper divisors (49541).

21165979 is an equidigital number, since it uses as much as digits as its factorization.

21165979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49540.

The product of its digits is 34020, while the sum is 40.

The square root of 21165979 is about 4600.6498454023. The cubic root of 21165979 is about 276.6173736797.

The spelling of 21165979 in words is "twenty-one million, one hundred sixty-five thousand, nine hundred seventy-nine".