20170561 has 4 divisors (see below), whose sum is σ = 20189952. Its totient is φ = 20151172.

The previous prime is 20170547. The next prime is 20170607. The reversal of 20170561 is 16507102.

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 not a de Polignac number, because 20170561 - 2⁷ = 20170433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20170511) 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, 8041 + ... + 10246.

It is an arithmetic number, because the mean of its divisors is an integer number (5047488).

Almost surely, 2^20170561 is an apocalyptic number.

It is an amenable number.

20170561 is a deficient number, since it is larger than the sum of its proper divisors (19391).

20170561 is a wasteful number, since it uses less digits than its factorization.

20170561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19390.

The product of its (nonzero) digits is 420, while the sum is 22.

The square root of 20170561 is about 4491.1647709698. The cubic root of 20170561 is about 272.2112014851.

Adding to 20170561 its reverse (16507102), we get a palindrome (36677663).

The spelling of 20170561 in words is "twenty million, one hundred seventy thousand, five hundred sixty-one".