20925809 has 4 divisors (see below), whose sum is σ = 21085680. Its totient is φ = 20765940.

The previous prime is 20925799. The next prime is 20925811. The reversal of 20925809 is 90852902.

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-20925809 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20925829) 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, 79739 + ... + 80000.

It is an arithmetic number, because the mean of its divisors is an integer number (5271420).

Almost surely, 2^20925809 is an apocalyptic number.

It is an amenable number.

20925809 is a deficient number, since it is larger than the sum of its proper divisors (159871).

20925809 is a wasteful number, since it uses less digits than its factorization.

20925809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159870.

The product of its (nonzero) digits is 12960, while the sum is 35.

The square root of 20925809 is about 4574.4736309219. The cubic root of 20925809 is about 275.5671337258.

The spelling of 20925809 in words is "twenty million, nine hundred twenty-five thousand, eight hundred nine".