27391981 has 4 divisors (see below), whose sum is σ = 29003292. Its totient is φ = 25780672.

The previous prime is 27391967. The next prime is 27391993. The reversal of 27391981 is 18919372.

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 10458756 + 16933225 = 3234^2 + 4115^2 .

It is a cyclic number.

It is not a de Polignac number, because 27391981 - 2¹³ = 27383789 is a prime.

It is a super-2 number, since 2×27391981² = 1500641246208722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27391961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 805630 + ... + 805663.

It is an arithmetic number, because the mean of its divisors is an integer number (7250823).

Almost surely, 2^27391981 is an apocalyptic number.

It is an amenable number.

27391981 is a deficient number, since it is larger than the sum of its proper divisors (1611311).

27391981 is a wasteful number, since it uses less digits than its factorization.

27391981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1611310.

The product of its digits is 27216, while the sum is 40.

The square root of 27391981 is about 5233.7348996677. The cubic root of 27391981 is about 301.4448120383. Note that the first 3 decimals are identical.

The spelling of 27391981 in words is "twenty-seven million, three hundred ninety-one thousand, nine hundred eighty-one".