21987287688671 has 2 divisors, whose sum is σ = 21987287688672. Its totient is φ = 21987287688670.

The previous prime is 21987287688649. The next prime is 21987287688677. The reversal of 21987287688671 is 17688678278912.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21987287688671 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21987287688677) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10993643844335 + 10993643844336.

It is an arithmetic number, because the mean of its divisors is an integer number (10993643844336).

Almost surely, 2^{21987287688671} is an apocalyptic number.

21987287688671 is a deficient number, since it is larger than the sum of its proper divisors (1).

21987287688671 is an equidigital number, since it uses as much as digits as its factorization.

21987287688671 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1820786688, while the sum is 80.

The spelling of 21987287688671 in words is "twenty-one trillion, nine hundred eighty-seven billion, two hundred eighty-seven million, six hundred eighty-eight thousand, six hundred seventy-one".