9981990 has 48 divisors (see below), whose sum is σ = 26131248. Its totient is φ = 2643648.

The previous prime is 9981943. The next prime is 9982051. The reversal of 9981990 is 991899.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 17449 + ... + 18011.

It is an arithmetic number, because the mean of its divisors is an integer number (544401).

Almost surely, 2^9981990 is an apocalyptic number.

9981990 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 9981990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (13065624).

9981990 is an abundant number, since it is smaller than the sum of its proper divisors (16149258).

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

9981990 is a wasteful number, since it uses less digits than its factorization.

9981990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 773 (or 770 counting only the distinct ones).

The product of its (nonzero) digits is 52488, while the sum is 45.

The square root of 9981990 is about 3159.4287458337. The cubic root of 9981990 is about 215.3140533837.

The spelling of 9981990 in words is "nine million, nine hundred eighty-one thousand, nine hundred ninety".