18791200561 has 9 divisors (see below), whose sum is σ = 21860267961. Its totient is φ = 16105920852.

The previous prime is 18791200517. The next prime is 18791200633. The reversal of 18791200561 is 16500219781.

It is a happy number.

The square root of 18791200561 is 137081.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 18791200561 - 2¹⁷ = 18791069489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18791200511) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 949776 + ... + 969358.

Almost surely, 2^18791200561 is an apocalyptic number.

18791200561 is the 137081-st square number.

18791200561 is the 68541-st centered octagonal number.

It is an amenable number.

18791200561 is a deficient number, since it is larger than the sum of its proper divisors (3069067400).

18791200561 is an frugal number, since it uses more digits than its factorization.

18791200561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39180 (or 19590 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 40.

The spelling of 18791200561 in words is "eighteen billion, seven hundred ninety-one million, two hundred thousand, five hundred sixty-one".