21209079 has 16 divisors (see below), whose sum is σ = 29030400. Its totient is φ = 13766880.

The previous prime is 21209077. The next prime is 21209093. The reversal of 21209079 is 97090212.

It is not a de Polignac number, because 21209079 - 2¹ = 21209077 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21209077) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48994 + ... + 49424.

It is an arithmetic number, because the mean of its divisors is an integer number (1814400).

Almost surely, 2^21209079 is an apocalyptic number.

21209079 is a deficient number, since it is larger than the sum of its proper divisors (7821321).

21209079 is a wasteful number, since it uses less digits than its factorization.

21209079 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 830.

The product of its (nonzero) digits is 2268, while the sum is 30.

The square root of 21209079 is about 4605.3315841533. The cubic root of 21209079 is about 276.8050038007.

The spelling of 21209079 in words is "twenty-one million, two hundred nine thousand, seventy-nine".