9987891280 has 20 divisors (see below), whose sum is σ = 23221847412. Its totient is φ = 3995156480.

The previous prime is 9987891269. The next prime is 9987891281. The reversal of 9987891280 is 821987899.

It can be written as a sum of positive squares in 2 ways, for example, as 4619105296 + 5368785984 = 67964^2 + 73272^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×9987891280² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9987891281) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 62424241 + ... + 62424400.

Almost surely, 2^9987891280 is an apocalyptic number.

It is an amenable number.

9987891280 is an abundant number, since it is smaller than the sum of its proper divisors (13233956132).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

9987891280 is a wasteful number, since it uses less digits than its factorization.

9987891280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124848654 (or 124848648 counting only the distinct ones).

The product of its (nonzero) digits is 5225472, while the sum is 61.

The square root of 9987891280 is about 99939.4380612579. The cubic root of 9987891280 is about 2153.5647572643.

The spelling of 9987891280 in words is "nine billion, nine hundred eighty-seven million, eight hundred ninety-one thousand, two hundred eighty".