20990309 has 4 divisors (see below), whose sum is σ = 21003360. Its totient is φ = 20977260.

The previous prime is 20990303. The next prime is 20990311. The reversal of 20990309 is 90309902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20990309 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20990303) 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, 3707 + ... + 7464.

It is an arithmetic number, because the mean of its divisors is an integer number (5250840).

Almost surely, 2^20990309 is an apocalyptic number.

It is an amenable number.

20990309 is a deficient number, since it is larger than the sum of its proper divisors (13051).

20990309 is a wasteful number, since it uses less digits than its factorization.

20990309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13050.

The product of its (nonzero) digits is 4374, while the sum is 32.

The square root of 20990309 is about 4581.5181981522. The cubic root of 20990309 is about 275.8499718476.

The spelling of 20990309 in words is "twenty million, nine hundred ninety thousand, three hundred nine".