1888721561 has 2 divisors, whose sum is σ = 1888721562. Its totient is φ = 1888721560.

The previous prime is 1888721519. The next prime is 1888721591. The reversal of 1888721561 is 1651278881.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1225350025 + 663371536 = 35005^2 + 25756^2 .

It is a cyclic number.

It is not a de Polignac number, because 1888721561 - 2²² = 1884527257 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1888721591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 944360780 + 944360781.

It is an arithmetic number, because the mean of its divisors is an integer number (944360781).

Almost surely, 2^1888721561 is an apocalyptic number.

It is an amenable number.

1888721561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1888721561 is an equidigital number, since it uses as much as digits as its factorization.

1888721561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 215040, while the sum is 47.

The square root of 1888721561 is about 43459.4243058971. The cubic root of 1888721561 is about 1236.1067539486.

The spelling of 1888721561 in words is "one billion, eight hundred eighty-eight million, seven hundred twenty-one thousand, five hundred sixty-one".