27991421 has 4 divisors (see below), whose sum is σ = 28003392. Its totient is φ = 27979452.

The previous prime is 27991399. The next prime is 27991477. The reversal of 27991421 is 12419972.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 27991421 - 2¹⁸ = 27729277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27991121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1205 + ... + 7578.

It is an arithmetic number, because the mean of its divisors is an integer number (7000848).

Almost surely, 2^27991421 is an apocalyptic number.

It is an amenable number.

27991421 is a deficient number, since it is larger than the sum of its proper divisors (11971).

27991421 is an equidigital number, since it uses as much as digits as its factorization.

27991421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11970.

The product of its digits is 9072, while the sum is 35.

The square root of 27991421 is about 5290.6919207227. The cubic root of 27991421 is about 303.6278810473.

The spelling of 27991421 in words is "twenty-seven million, nine hundred ninety-one thousand, four hundred twenty-one".