20317561 has 4 divisors (see below), whose sum is σ = 22164624. Its totient is φ = 18470500.

The previous prime is 20317559. The next prime is 20317571. The reversal of 20317561 is 16571302.

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 20317561 - 2¹ = 20317559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20317501) 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, 923515 + ... + 923536.

It is an arithmetic number, because the mean of its divisors is an integer number (5541156).

Almost surely, 2^20317561 is an apocalyptic number.

It is an amenable number.

20317561 is a deficient number, since it is larger than the sum of its proper divisors (1847063).

20317561 is a wasteful number, since it uses less digits than its factorization.

20317561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1847062.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 20317561 is about 4507.5005268996. The cubic root of 20317561 is about 272.8708795579.

Adding to 20317561 its reverse (16571302), we get a palindrome (36888863).

The spelling of 20317561 in words is "twenty million, three hundred seventeen thousand, five hundred sixty-one".