20561909 has 8 divisors (see below), whose sum is σ = 20799360. Its totient is φ = 20326176.

The previous prime is 20561903. The next prime is 20561911. The reversal of 20561909 is 90916502.

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 20561909 - 2¹² = 20557813 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 (20561903) 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, 55844 + ... + 56210.

It is an arithmetic number, because the mean of its divisors is an integer number (2599920).

Almost surely, 2^20561909 is an apocalyptic number.

It is an amenable number.

20561909 is a deficient number, since it is larger than the sum of its proper divisors (237451).

20561909 is a wasteful number, since it uses less digits than its factorization.

20561909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 859.

The product of its (nonzero) digits is 4860, while the sum is 32.

The square root of 20561909 is about 4534.5241205666. The cubic root of 20561909 is about 273.9604121682.

The spelling of 20561909 in words is "twenty million, five hundred sixty-one thousand, nine hundred nine".