21198709 has 16 divisors (see below), whose sum is σ = 25420032. Its totient is φ = 17284608.

The previous prime is 21198701. The next prime is 21198719. The reversal of 21198709 is 90789112.

It is a cyclic number.

It is not a de Polignac number, because 21198709 - 2³ = 21198701 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21198701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56647 + ... + 57019.

It is an arithmetic number, because the mean of its divisors is an integer number (1588752).

Almost surely, 2^21198709 is an apocalyptic number.

It is an amenable number.

21198709 is a deficient number, since it is larger than the sum of its proper divisors (4221323).

21198709 is a wasteful number, since it uses less digits than its factorization.

21198709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 756.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 21198709 is about 4604.2055775128. The cubic root of 21198709 is about 276.7598826233.

The spelling of 21198709 in words is "twenty-one million, one hundred ninety-eight thousand, seven hundred nine".