19887187121 has 24 divisors (see below), whose sum is σ = 21379138344. Its totient is φ = 18491639040.

The previous prime is 19887187109. The next prime is 19887187123. The reversal of 19887187121 is 12178178891.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 485761600 + 19401425521 = 22040^2 + 139289^2 .

It is not a de Polignac number, because 19887187121 - 2²² = 19882992817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (19887187123) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 16669301 + ... + 16670493.

It is an arithmetic number, because the mean of its divisors is an integer number (890797431).

Almost surely, 2^19887187121 is an apocalyptic number.

It is an amenable number.

19887187121 is a deficient number, since it is larger than the sum of its proper divisors (1491951223).

19887187121 is a wasteful number, since it uses less digits than its factorization.

19887187121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2049 (or 2030 counting only the distinct ones).

The product of its digits is 451584, while the sum is 53.

The spelling of 19887187121 in words is "nineteen billion, eight hundred eighty-seven million, one hundred eighty-seven thousand, one hundred twenty-one".