1803812908661 has 4 divisors (see below), whose sum is σ = 1803816109932. Its totient is φ = 1803809707392.

The previous prime is 1803812908627. The next prime is 1803812908697. The reversal of 1803812908661 is 1668092183081.

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 1724181712561 + 79631196100 = 1313081^2 + 282190^2 .

It is a cyclic number.

It is not a de Polignac number, because 1803812908661 - 2³⁸ = 1528935001717 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 (1803812908561) 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, 505820 + ... + 1965573.

It is an arithmetic number, because the mean of its divisors is an integer number (450954027483).

Almost surely, 2^{1803812908661} is an apocalyptic number.

It is an amenable number.

1803812908661 is a deficient number, since it is larger than the sum of its proper divisors (3201271).

1803812908661 is an equidigital number, since it uses as much as digits as its factorization.

1803812908661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3201270.

The product of its (nonzero) digits is 995328, while the sum is 53.

The spelling of 1803812908661 in words is "one trillion, eight hundred three billion, eight hundred twelve million, nine hundred eight thousand, six hundred sixty-one".