12561663991401 has 24 divisors (see below), whose sum is σ = 20950495739264. Its totient is φ = 7104092739840.

The previous prime is 12561663991397. The next prime is 12561663991427. The reversal of 12561663991401 is 10419936616521.

12561663991401 is a `hidden beast` number, since 1 + 2 + 5 + 61 + 66 + 39 + 91 + 401 = 666.

It is not a de Polignac number, because 12561663991401 - 2² = 12561663991397 is a prime.

It is not an unprimeable number, because it can be changed into a prime (12561663941401) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1027785085 + ... + 1027797306.

Almost surely, 2^{12561663991401} is an apocalyptic number.

It is an amenable number.

12561663991401 is a deficient number, since it is larger than the sum of its proper divisors (8388831747863).

12561663991401 is a wasteful number, since it uses less digits than its factorization.

12561663991401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2055582501 (or 2055582498 counting only the distinct ones).

The product of its (nonzero) digits is 2099520, while the sum is 54.

The spelling of 12561663991401 in words is "twelve trillion, five hundred sixty-one billion, six hundred sixty-three million, nine hundred ninety-one thousand, four hundred one".