19981656 has 48 divisors (see below), whose sum is σ = 54437760. Its totient is φ = 6621120.

The previous prime is 19981649. The next prime is 19981693. The reversal of 19981656 is 65618991.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13026 + ... + 14478.

It is an arithmetic number, because the mean of its divisors is an integer number (1134120).

Almost surely, 2^19981656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19981656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27218880).

19981656 is an abundant number, since it is smaller than the sum of its proper divisors (34456104).

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

19981656 is a wasteful number, since it uses less digits than its factorization.

19981656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1656 (or 1649 counting only the distinct ones).

The product of its digits is 116640, while the sum is 45.

The square root of 19981656 is about 4470.0845629585. The cubic root of 19981656 is about 271.3587474795.

The spelling of 19981656 in words is "nineteen million, nine hundred eighty-one thousand, six hundred fifty-six".