1261016646561 has 32 divisors (see below), whose sum is σ = 2136711417600. Its totient is φ = 720021778560.

The previous prime is 1261016646541. The next prime is 1261016646581. The reversal of 1261016646561 is 1656466101621.

1261016646561 is a `hidden beast` number, since 1 + 2 + 6 + 10 + 16 + 64 + 6 + 561 = 666.

It is an interprime number because it is at equal distance from previous prime (1261016646541) and next prime (1261016646581).

It is not a de Polignac number, because 1261016646561 - 2⁷ = 1261016646433 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1261016646511) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2344450 + ... + 2831691.

It is an arithmetic number, because the mean of its divisors is an integer number (66772231800).

Almost surely, 2^{1261016646561} is an apocalyptic number.

It is an amenable number.

1261016646561 is a deficient number, since it is larger than the sum of its proper divisors (875694771039).

1261016646561 is a wasteful number, since it uses less digits than its factorization.

1261016646561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5177446 (or 5177440 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The spelling of 1261016646561 in words is "one trillion, two hundred sixty-one billion, sixteen million, six hundred forty-six thousand, five hundred sixty-one".