206015561 has 4 divisors (see below), whose sum is σ = 206048532. Its totient is φ = 205982592.

The previous prime is 206015549. The next prime is 206015581. The reversal of 206015561 is 165510602.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 24601600 + 181413961 = 4960^2 + 13469^2 .

It is a cyclic number.

It is not a de Polignac number, because 206015561 - 2⁶ = 206015497 is a prime.

It is a super-2 number, since 2×206015561² = 84884822748289442, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 206015561.

It is not an unprimeable number, because it can be changed into a prime (206015501) 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, 3920 + ... + 20673.

It is an arithmetic number, because the mean of its divisors is an integer number (51512133).

Almost surely, 2^206015561 is an apocalyptic number.

It is an amenable number.

206015561 is a deficient number, since it is larger than the sum of its proper divisors (32971).

206015561 is an equidigital number, since it uses as much as digits as its factorization.

206015561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32970.

The product of its (nonzero) digits is 1800, while the sum is 26.

The square root of 206015561 is about 14353.2421772922. The cubic root of 206015561 is about 590.6089289171.

It can be divided in two parts, 20601 and 5561, that added together give a palindrome (26162).

The spelling of 206015561 in words is "two hundred six million, fifteen thousand, five hundred sixty-one".