21391179 has 4 divisors (see below), whose sum is σ = 28521576. Its totient is φ = 14260784.

The previous prime is 21391133. The next prime is 21391187. The reversal of 21391179 is 97119312.

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 21391179 - 2¹² = 21387083 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21391129) 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, 3565194 + ... + 3565199.

It is an arithmetic number, because the mean of its divisors is an integer number (7130394).

Almost surely, 2^21391179 is an apocalyptic number.

21391179 is a deficient number, since it is larger than the sum of its proper divisors (7130397).

21391179 is an equidigital number, since it uses as much as digits as its factorization.

21391179 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7130396.

The product of its digits is 3402, while the sum is 33.

The square root of 21391179 is about 4625.0598915041. The cubic root of 21391179 is about 277.5949581687.

The spelling of 21391179 in words is "twenty-one million, three hundred ninety-one thousand, one hundred seventy-nine".