20311561 has 8 divisors (see below), whose sum is σ = 20835144. Its totient is φ = 19793280.

The previous prime is 20311559. The next prime is 20311591. The reversal of 20311561 is 16511302.

It can be written as a sum of positive squares in 4 ways, for example, as 553536 + 19758025 = 744^2 + 4445^2 .

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 20311561 - 2¹ = 20311559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20311591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7101 + ... + 9541.

It is an arithmetic number, because the mean of its divisors is an integer number (2604393).

Almost surely, 2^20311561 is an apocalyptic number.

It is an amenable number.

20311561 is a deficient number, since it is larger than the sum of its proper divisors (523583).

20311561 is a wasteful number, since it uses less digits than its factorization.

20311561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2651.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 20311561 is about 4506.8349204292. The cubic root of 20311561 is about 272.8440163193.

Adding to 20311561 its reverse (16511302), we get a palindrome (36822863).

The spelling of 20311561 in words is "twenty million, three hundred eleven thousand, five hundred sixty-one".