27821991 has 16 divisors (see below), whose sum is σ = 38592000. Its totient is φ = 17807328.

The previous prime is 27821987. The next prime is 27821993. The reversal of 27821991 is 19912872.

It is not a de Polignac number, because 27821991 - 2² = 27821987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27821993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16510 + ... + 18116.

It is an arithmetic number, because the mean of its divisors is an integer number (2412000).

Almost surely, 2^27821991 is an apocalyptic number.

27821991 is a deficient number, since it is larger than the sum of its proper divisors (10770009).

27821991 is a wasteful number, since it uses less digits than its factorization.

27821991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1838.

The product of its digits is 18144, while the sum is 39.

The square root of 27821991 is about 5274.6555337766. The cubic root of 27821991 is about 303.0140284762.

The spelling of 27821991 in words is "twenty-seven million, eight hundred twenty-one thousand, nine hundred ninety-one".