27981999 has 6 divisors (see below), whose sum is σ = 40418456. Its totient is φ = 18654660.

The previous prime is 27981997. The next prime is 27982001. The reversal of 27981999 is 99918972.

It is an interprime number because it is at equal distance from previous prime (27981997) and next prime (27982001).

It is not a de Polignac number, because 27981999 - 2¹ = 27981997 is a prime.

It is a super-3 number, since 3×27981999³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27981991) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1554547 + ... + 1554564.

Almost surely, 2^27981999 is an apocalyptic number.

27981999 is a deficient number, since it is larger than the sum of its proper divisors (12436457).

27981999 is a wasteful number, since it uses less digits than its factorization.

27981999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3109117 (or 3109114 counting only the distinct ones).

The product of its digits is 734832, while the sum is 54.

The square root of 27981999 is about 5289.8014140419. The cubic root of 27981999 is about 303.5938098588.

Adding to 27981999 its product of digits (734832), we get a triangular number (28716831 = T₇₅₇₈).

The spelling of 27981999 in words is "twenty-seven million, nine hundred eighty-one thousand, nine hundred ninety-nine".