21208817587 has 2 divisors, whose sum is σ = 21208817588. Its totient is φ = 21208817586.

The previous prime is 21208817549. The next prime is 21208817629. The reversal of 21208817587 is 78571880212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21208817587 - 2¹¹ = 21208815539 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21208817587.

It is not a weakly prime, because it can be changed into another prime (21208817537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10604408793 + 10604408794.

It is an arithmetic number, because the mean of its divisors is an integer number (10604408794).

Almost surely, 2^21208817587 is an apocalyptic number.

21208817587 is a deficient number, since it is larger than the sum of its proper divisors (1).

21208817587 is an equidigital number, since it uses as much as digits as its factorization.

21208817587 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 501760, while the sum is 49.

The spelling of 21208817587 in words is "twenty-one billion, two hundred eight million, eight hundred seventeen thousand, five hundred eighty-seven".