27981221 has 2 divisors, whose sum is σ = 27981222. Its totient is φ = 27981220.

The previous prime is 27981211. The next prime is 27981263. The reversal of 27981221 is 12218972.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27196225 + 784996 = 5215^2 + 886^2 .

It is a cyclic number.

It is not a de Polignac number, because 27981221 - 2¹⁴ = 27964837 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (27981211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13990610 + 13990611.

It is an arithmetic number, because the mean of its divisors is an integer number (13990611).

Almost surely, 2^27981221 is an apocalyptic number.

It is an amenable number.

27981221 is a deficient number, since it is larger than the sum of its proper divisors (1).

27981221 is an equidigital number, since it uses as much as digits as its factorization.

27981221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 32.

The square root of 27981221 is about 5289.7278757985. The cubic root of 27981221 is about 303.5909961669.

The spelling of 27981221 in words is "twenty-seven million, nine hundred eighty-one thousand, two hundred twenty-one".