203661566861 has 4 divisors (see below), whose sum is σ = 203803690812. Its totient is φ = 203519442912.

The previous prime is 203661566851. The next prime is 203661566881. The reversal of 203661566861 is 168665166302.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 168665166302 = 2 ⋅84332583151.

It can be written as a sum of positive squares in 2 ways, for example, as 82136120836 + 121525446025 = 286594^2 + 348605^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-203661566861 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (203661566851) 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, 71059826 + ... + 71062691.

It is an arithmetic number, because the mean of its divisors is an integer number (50950922703).

Almost surely, 2^203661566861 is an apocalyptic number.

It is an amenable number.

203661566861 is a deficient number, since it is larger than the sum of its proper divisors (142123951).

203661566861 is a wasteful number, since it uses less digits than its factorization.

203661566861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142123950.

The product of its (nonzero) digits is 1866240, while the sum is 50.

The spelling of 203661566861 in words is "two hundred three billion, six hundred sixty-one million, five hundred sixty-six thousand, eight hundred sixty-one".