27991121 has 2 divisors, whose sum is σ = 27991122. Its totient is φ = 27991120.

The previous prime is 27991099. The next prime is 27991147. The reversal of 27991121 is 12119972.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20151121 + 7840000 = 4489^2 + 2800^2 .

It is a cyclic number.

It is not a de Polignac number, because 27991121 - 2⁶ = 27991057 is a prime.

It is not a weakly prime, because it can be changed into another prime (27997121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13995560 + 13995561.

It is an arithmetic number, because the mean of its divisors is an integer number (13995561).

Almost surely, 2^27991121 is an apocalyptic number.

It is an amenable number.

27991121 is a deficient number, since it is larger than the sum of its proper divisors (1).

27991121 is an equidigital number, since it uses as much as digits as its factorization.

27991121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2268, while the sum is 32.

The square root of 27991121 is about 5290.6635689675. The cubic root of 27991121 is about 303.6267963258.

The spelling of 27991121 in words is "twenty-seven million, nine hundred ninety-one thousand, one hundred twenty-one".