18681962561 has 2 divisors, whose sum is σ = 18681962562. Its totient is φ = 18681962560.

The previous prime is 18681962557. The next prime is 18681962569. The reversal of 18681962561 is 16526918681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12790479025 + 5891483536 = 113095^2 + 76756^2 .

It is a cyclic number.

It is not a de Polignac number, because 18681962561 - 2² = 18681962557 is a prime.

It is not a weakly prime, because it can be changed into another prime (18681962569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9340981280 + 9340981281.

It is an arithmetic number, because the mean of its divisors is an integer number (9340981281).

Almost surely, 2^18681962561 is an apocalyptic number.

It is an amenable number.

18681962561 is a deficient number, since it is larger than the sum of its proper divisors (1).

18681962561 is an equidigital number, since it uses as much as digits as its factorization.

18681962561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1244160, while the sum is 53.

The spelling of 18681962561 in words is "eighteen billion, six hundred eighty-one million, nine hundred sixty-two thousand, five hundred sixty-one".