19881540 has 144 divisors (see below), whose sum is σ = 71285760. Its totient is φ = 4389120.

The previous prime is 19881503. The next prime is 19881541. The reversal of 19881540 is 4518891.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 19881495 and 19881504.

It is not an unprimeable number, because it can be changed into a prime (19881541) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 38806 + ... + 39314.

It is an arithmetic number, because the mean of its divisors is an integer number (495040).

Almost surely, 2^19881540 is an apocalyptic number.

19881540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19881540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35642880).

19881540 is an abundant number, since it is smaller than the sum of its proper divisors (51404220).

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

19881540 is a wasteful number, since it uses less digits than its factorization.

19881540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 562 (or 557 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 19881540 is about 4458.8720546793. The cubic root of 19881540 is about 270.9047835681.

The spelling of 19881540 in words is "nineteen million, eight hundred eighty-one thousand, five hundred forty".