1561515221601 has 12 divisors (see below), whose sum is σ = 2333298607380. Its totient is φ = 1005113245920.

The previous prime is 1561515221549. The next prime is 1561515221621. The reversal of 1561515221601 is 1061225151651.

1561515221601 is a `hidden beast` number, since 1 + 5 + 6 + 15 + 15 + 2 + 21 + 601 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 645620285025 + 915894936576 = 803505^2 + 957024^2 .

It is not a de Polignac number, because 1561515221601 - 2²¹ = 1561513124449 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1561515221621) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2991408210 + ... + 2991408731.

It is an arithmetic number, because the mean of its divisors is an integer number (194441550615).

Almost surely, 2^{1561515221601} is an apocalyptic number.

It is an amenable number.

1561515221601 is a deficient number, since it is larger than the sum of its proper divisors (771783385779).

1561515221601 is a wasteful number, since it uses less digits than its factorization.

1561515221601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5982816976 (or 5982816973 counting only the distinct ones).

The product of its (nonzero) digits is 18000, while the sum is 36.

The spelling of 1561515221601 in words is "one trillion, five hundred sixty-one billion, five hundred fifteen million, two hundred twenty-one thousand, six hundred one".