398181561885661 has 2 divisors, whose sum is σ = 398181561885662. Its totient is φ = 398181561885660.

The previous prime is 398181561885643. The next prime is 398181561885673. The reversal of 398181561885661 is 166588165181893.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 350124348792100 + 48057213093561 = 18711610^2 + 6932331^2 .

It is a cyclic number.

It is not a de Polignac number, because 398181561885661 - 2²⁹ = 398181025014749 is a prime.

It is a super-3 number, since 3×398181561885661³ (a number of 45 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (398181561888661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199090780942830 + 199090780942831.

It is an arithmetic number, because the mean of its divisors is an integer number (199090780942831).

Almost surely, 2^{398181561885661} is an apocalyptic number.

It is an amenable number.

398181561885661 is a deficient number, since it is larger than the sum of its proper divisors (1).

398181561885661 is an equidigital number, since it uses as much as digits as its factorization.

398181561885661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 597196800, while the sum is 76.

The spelling of 398181561885661 in words is "three hundred ninety-eight trillion, one hundred eighty-one billion, five hundred sixty-one million, eight hundred eighty-five thousand, six hundred sixty-one".