19749840 has 80 divisors (see below), whose sum is σ = 66799296. Its totient is φ = 4787200.

The previous prime is 19749833. The next prime is 19749859. The reversal of 19749840 is 4894791.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 19749792 and 19749801.

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 15 ways as a sum of consecutive naturals, for example, 1101 + ... + 6380.

Almost surely, 2^19749840 is an apocalyptic number.

19749840 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 19749840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33399648).

19749840 is an abundant number, since it is smaller than the sum of its proper divisors (47049456).

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

19749840 is a wasteful number, since it uses less digits than its factorization.

19749840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7508 (or 7502 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 42.

The square root of 19749840 is about 4444.0792072149. The cubic root of 19749840 is about 270.3052788453.

The spelling of 19749840 in words is "nineteen million, seven hundred forty-nine thousand, eight hundred forty".