19978409 has 16 divisors (see below), whose sum is σ = 22588416. Its totient is φ = 17510400.

The previous prime is 19978393. The next prime is 19978457. The reversal of 19978409 is 90487991.

It is a cyclic number.

It is not a de Polignac number, because 19978409 - 2⁴ = 19978393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19978109) 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 15 ways as a sum of consecutive naturals, for example, 77609 + ... + 77865.

It is an arithmetic number, because the mean of its divisors is an integer number (1411776).

Almost surely, 2^19978409 is an apocalyptic number.

It is an amenable number.

19978409 is a deficient number, since it is larger than the sum of its proper divisors (2610007).

19978409 is a wasteful number, since it uses less digits than its factorization.

19978409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 496.

The product of its (nonzero) digits is 163296, while the sum is 47.

The square root of 19978409 is about 4469.7213559684. The cubic root of 19978409 is about 271.3440481709.

The spelling of 19978409 in words is "nineteen million, nine hundred seventy-eight thousand, four hundred nine".