20731998 has 48 divisors (see below), whose sum is σ = 48657024. Its totient is φ = 5871600.

The previous prime is 20731987. The next prime is 20732003. The reversal of 20731998 is 89913702.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 44161 + ... + 44627.

It is an arithmetic number, because the mean of its divisors is an integer number (1013688).

Almost surely, 2^20731998 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20731998, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24328512).

20731998 is an abundant number, since it is smaller than the sum of its proper divisors (27925026).

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

20731998 is a wasteful number, since it uses less digits than its factorization.

20731998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 637 (or 630 counting only the distinct ones).

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 20731998 is about 4553.2403846052. The cubic root of 20731998 is about 274.7137428997.

The spelling of 20731998 in words is "twenty million, seven hundred thirty-one thousand, nine hundred ninety-eight".