20001561 has 8 divisors (see below), whose sum is σ = 27588480. Its totient is φ = 12874512.

The previous prime is 20001557. The next prime is 20001613. The reversal of 20001561 is 16510002.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20001561 - 2² = 20001557 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20001561.

It is not an unprimeable number, because it can be changed into a prime (20001521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 114865 + ... + 115038.

It is an arithmetic number, because the mean of its divisors is an integer number (3448560).

Almost surely, 2^20001561 is an apocalyptic number.

It is an amenable number.

20001561 is a deficient number, since it is larger than the sum of its proper divisors (7586919).

20001561 is a wasteful number, since it uses less digits than its factorization.

20001561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229935.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 20001561 is about 4472.3104766999. The cubic root of 20001561 is about 271.4488234856.

Adding to 20001561 its reverse (16510002), we get a palindrome (36511563).

The spelling of 20001561 in words is "twenty million, one thousand, five hundred sixty-one".