21987287688651 has 16 divisors (see below), whose sum is σ = 29464125737760. Its totient is φ = 14584406469120.

The previous prime is 21987287688649. The next prime is 21987287688671. The reversal of 21987287688651 is 15688678278912.

It is not a de Polignac number, because 21987287688651 - 2¹ = 21987287688649 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21987287688671) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9692590 + ... + 11743971.

It is an arithmetic number, because the mean of its divisors is an integer number (1841507858610).

Almost surely, 2^{21987287688651} is an apocalyptic number.

21987287688651 is a deficient number, since it is larger than the sum of its proper divisors (7476838049109).

21987287688651 is a wasteful number, since it uses less digits than its factorization.

21987287688651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21438286.

The product of its digits is 1300561920, while the sum is 78.

The spelling of 21987287688651 in words is "twenty-one trillion, nine hundred eighty-seven billion, two hundred eighty-seven million, six hundred eighty-eight thousand, six hundred fifty-one".