21987287688650 has 12 divisors (see below), whose sum is σ = 40896355100982. Its totient is φ = 8794915075440.

The previous prime is 21987287688649. The next prime is 21987287688671. The reversal of 21987287688650 is 5688678278912.

It can be written as a sum of positive squares in 3 ways, for example, as 11025248744041 + 10962038944609 = 3320429^2 + 3310897^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 219872876837 + ... + 219872876936.

Almost surely, 2^{21987287688650} is an apocalyptic number.

21987287688650 is a deficient number, since it is larger than the sum of its proper divisors (18909067412332).

21987287688650 is a wasteful number, since it uses less digits than its factorization.

21987287688650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 439745753785 (or 439745753780 counting only the distinct ones).

The product of its (nonzero) digits is 1300561920, while the sum is 77.

The spelling of 21987287688650 in words is "twenty-one trillion, nine hundred eighty-seven billion, two hundred eighty-seven million, six hundred eighty-eight thousand, six hundred fifty".