18861863561 has 2 divisors, whose sum is σ = 18861863562. Its totient is φ = 18861863560.

The previous prime is 18861863551. The next prime is 18861863591. The reversal of 18861863561 is 16536816881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13544537161 + 5317326400 = 116381^2 + 72920^2 .

It is a cyclic number.

It is not a de Polignac number, because 18861863561 - 2²⁶ = 18794754697 is a prime.

It is not a weakly prime, because it can be changed into another prime (18861863551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9430931780 + 9430931781.

It is an arithmetic number, because the mean of its divisors is an integer number (9430931781).

Almost surely, 2^18861863561 is an apocalyptic number.

It is an amenable number.

18861863561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18861863561 is an equidigital number, since it uses as much as digits as its factorization.

18861863561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1658880, while the sum is 53.

The spelling of 18861863561 in words is "eighteen billion, eight hundred sixty-one million, eight hundred sixty-three thousand, five hundred sixty-one".