1981163521 has 4 divisors (see below), whose sum is σ = 1983269844. Its totient is φ = 1979057200.

The previous prime is 1981163519. The next prime is 1981163533. The reversal of 1981163521 is 1253611891.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1607127921 + 374035600 = 40089^2 + 19340^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981163521 - 2¹ = 1981163519 is a prime.

It is a super-3 number, since 3×1981163521³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981163021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1051750 + ... + 1053631.

It is an arithmetic number, because the mean of its divisors is an integer number (495817461).

Almost surely, 2^1981163521 is an apocalyptic number.

It is an amenable number.

1981163521 is a deficient number, since it is larger than the sum of its proper divisors (2106323).

1981163521 is an equidigital number, since it uses as much as digits as its factorization.

1981163521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2106322.

The product of its digits is 12960, while the sum is 37.

The square root of 1981163521 is about 44510.2630974026. The cubic root of 1981163521 is about 1255.9531541026.

The spelling of 1981163521 in words is "one billion, nine hundred eighty-one million, one hundred sixty-three thousand, five hundred twenty-one".