19988391 has 8 divisors (see below), whose sum is σ = 26673904. Its totient is φ = 13314240.

The previous prime is 19988383. The next prime is 19988411. The reversal of 19988391 is 19388991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 19988391 - 2³ = 19988383 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19988391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19988321) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2961 + ... + 6981.

It is an arithmetic number, because the mean of its divisors is an integer number (3334238).

Almost surely, 2^19988391 is an apocalyptic number.

19988391 is a deficient number, since it is larger than the sum of its proper divisors (6685513).

19988391 is a wasteful number, since it uses less digits than its factorization.

19988391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5681.

The product of its digits is 139968, while the sum is 48.

The square root of 19988391 is about 4470.8378409421. The cubic root of 19988391 is about 271.3892320377.

The spelling of 19988391 in words is "nineteen million, nine hundred eighty-eight thousand, three hundred ninety-one".