20031561 has 12 divisors (see below), whose sum is σ = 31565040. Its totient is φ = 12140280.

The previous prime is 20031533. The next prime is 20031563. The reversal of 20031561 is 16513002.

It is not a de Polignac number, because 20031561 - 2¹⁸ = 19769417 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20031563) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 101071 + ... + 101268.

It is an arithmetic number, because the mean of its divisors is an integer number (2630420).

Almost surely, 2^20031561 is an apocalyptic number.

It is an amenable number.

20031561 is a deficient number, since it is larger than the sum of its proper divisors (11533479).

20031561 is a wasteful number, since it uses less digits than its factorization.

20031561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 202356 (or 202353 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 20031561 is about 4475.6631910813. The cubic root of 20031561 is about 271.5844695097.

Adding to 20031561 its reverse (16513002), we get a palindrome (36544563).

The spelling of 20031561 in words is "twenty million, thirty-one thousand, five hundred sixty-one".