9891987 has 32 divisors (see below), whose sum is σ = 16051200. Its totient is φ = 5298048.

The previous prime is 9891953. The next prime is 9891991. The reversal of 9891987 is 7891989.

9891987 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 9891987 - 2⁶ = 9891923 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9891997) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 22314 + ... + 22752.

It is an arithmetic number, because the mean of its divisors is an integer number (501600).

Almost surely, 2^9891987 is an apocalyptic number.

9891987 is a deficient number, since it is larger than the sum of its proper divisors (6159213).

9891987 is a wasteful number, since it uses less digits than its factorization.

9891987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 515.

The product of its digits is 326592, while the sum is 51.

The square root of 9891987 is about 3145.1529374579. The cubic root of 9891987 is about 214.6649694558.

It can be divided in two parts, 9891 and 987, that added together give a triangular number (10878 = T₁₄₇).

The spelling of 9891987 in words is "nine million, eight hundred ninety-one thousand, nine hundred eighty-seven".