27987981 has 16 divisors (see below), whose sum is σ = 43234944. Its totient is φ = 15773184.

The previous prime is 27987961. The next prime is 27987989. The reversal of 27987981 is 18978972.

It is not a de Polignac number, because 27987981 - 2¹⁰ = 27986957 is a prime.

It is a super-3 number, since 3×27987981³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27987989) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7596 + ... + 10661.

It is an arithmetic number, because the mean of its divisors is an integer number (2702184).

Almost surely, 2^27987981 is an apocalyptic number.

27987981 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

27987981 is a deficient number, since it is larger than the sum of its proper divisors (15246963).

27987981 is a wasteful number, since it uses less digits than its factorization.

27987981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18340.

The product of its digits is 508032, while the sum is 51.

The square root of 27987981 is about 5290.3668114791. The cubic root of 27987981 is about 303.6154424421.

Subtracting from 27987981 its reverse (18978972), we obtain a palindrome (9009009).

The spelling of 27987981 in words is "twenty-seven million, nine hundred eighty-seven thousand, nine hundred eighty-one".