19978540 has 12 divisors (see below), whose sum is σ = 41954976. Its totient is φ = 7991408.

The previous prime is 19978487. The next prime is 19978549. The reversal of 19978540 is 4587991.

It is not an unprimeable number, because it can be changed into a prime (19978549) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 499444 + ... + 499483.

It is an arithmetic number, because the mean of its divisors is an integer number (3496248).

Almost surely, 2^19978540 is an apocalyptic number.

19978540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

19978540 is an abundant number, since it is smaller than the sum of its proper divisors (21976436).

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

19978540 is a wasteful number, since it uses less digits than its factorization.

19978540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 998936 (or 998934 counting only the distinct ones).

The product of its (nonzero) digits is 90720, while the sum is 43.

The square root of 19978540 is about 4469.7360101017. The cubic root of 19978540 is about 271.3446412444.

The spelling of 19978540 in words is "nineteen million, nine hundred seventy-eight thousand, five hundred forty".