27991808409557 has 2 divisors, whose sum is σ = 27991808409558. Its totient is φ = 27991808409556.

The previous prime is 27991808409533. The next prime is 27991808409619. The reversal of 27991808409557 is 75590480819972.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 26658231511921 + 1333576897636 = 5163161^2 + 1154806^2 .

It is a cyclic number.

It is not a de Polignac number, because 27991808409557 - 2¹² = 27991808405461 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (27991808409527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13995904204778 + 13995904204779.

It is an arithmetic number, because the mean of its divisors is an integer number (13995904204779).

Almost surely, 2^{27991808409557} is an apocalyptic number.

It is an amenable number.

27991808409557 is a deficient number, since it is larger than the sum of its proper divisors (1).

27991808409557 is an equidigital number, since it uses as much as digits as its factorization.

27991808409557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 457228800, while the sum is 74.

The spelling of 27991808409557 in words is "twenty-seven trillion, nine hundred ninety-one billion, eight hundred eight million, four hundred nine thousand, five hundred fifty-seven".