21920709 has 8 divisors (see below), whose sum is σ = 29357280. Its totient is φ = 14548976.

The previous prime is 21920693. The next prime is 21920711. The reversal of 21920709 is 90702912.

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 21920709 - 2⁴ = 21920693 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21920749) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15414 + ... + 16775.

It is an arithmetic number, because the mean of its divisors is an integer number (3669660).

Almost surely, 2^21920709 is an apocalyptic number.

It is an amenable number.

21920709 is a deficient number, since it is larger than the sum of its proper divisors (7436571).

21920709 is a wasteful number, since it uses less digits than its factorization.

21920709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32419.

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

The square root of 21920709 is about 4681.9556811230. The cubic root of 21920709 is about 279.8668967709.

The spelling of 21920709 in words is "twenty-one million, nine hundred twenty thousand, seven hundred nine".