19981501561566 has 24 divisors (see below), whose sum is σ = 45839915347824. Its totient is φ = 6268706372160.

The previous prime is 19981501561519. The next prime is 19981501561591. The reversal of 19981501561566 is 66516510518991.

19981501561566 is a `hidden beast` number, since 1 + 9 + 9 + 8 + 1 + 5 + 0 + 1 + 5 + 61 + 566 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32649512050 + ... + 32649512661.

It is an arithmetic number, because the mean of its divisors is an integer number (1909996472826).

Almost surely, 2^{19981501561566} is an apocalyptic number.

19981501561566 is an abundant number, since it is smaller than the sum of its proper divisors (25858413786258).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

19981501561566 is a wasteful number, since it uses less digits than its factorization.

19981501561566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65299024736 (or 65299024733 counting only the distinct ones).

The product of its (nonzero) digits is 17496000, while the sum is 63.

The spelling of 19981501561566 in words is "nineteen trillion, nine hundred eighty-one billion, five hundred one million, five hundred sixty-one thousand, five hundred sixty-six".