1981540365161 has 12 divisors (see below), whose sum is σ = 2384541890820. Its totient is φ = 1639895473440.

The previous prime is 1981540365151. The next prime is 1981540365163. The reversal of 1981540365161 is 1615630451891.

It can be written as a sum of positive squares in 2 ways, for example, as 1664954089561 + 316586275600 = 1290331^2 + 562660^2 .

It is not a de Polignac number, because 1981540365161 - 2¹⁰ = 1981540364137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981540365163) 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, 697233050 + ... + 697235891.

It is an arithmetic number, because the mean of its divisors is an integer number (198711824235).

Almost surely, 2^{1981540365161} is an apocalyptic number.

It is an amenable number.

1981540365161 is a deficient number, since it is larger than the sum of its proper divisors (403001525659).

1981540365161 is a wasteful number, since it uses less digits than its factorization.

1981540365161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1394468984 (or 1394468977 counting only the distinct ones).

The product of its (nonzero) digits is 777600, while the sum is 50.

The spelling of 1981540365161 in words is "one trillion, nine hundred eighty-one billion, five hundred forty million, three hundred sixty-five thousand, one hundred sixty-one".