19997856 has 72 divisors (see below), whose sum is σ = 59361120. Its totient is φ = 6374016.

The previous prime is 19997837. The next prime is 19997867. The reversal of 19997856 is 65879991.

It is a tau number, because it is divible by the number of its divisors (72).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5115 + ... + 8133.

It is an arithmetic number, because the mean of its divisors is an integer number (824460).

Almost surely, 2^19997856 is an apocalyptic number.

19997856 is a gapful number since it is divisible by the number (16) 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 19997856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29680560).

19997856 is an abundant number, since it is smaller than the sum of its proper divisors (39363264).

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

19997856 is a wasteful number, since it uses less digits than its factorization.

19997856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3058 (or 3047 counting only the distinct ones).

The product of its digits is 1224720, while the sum is 54.

The square root of 19997856 is about 4471.8962420879. The cubic root of 19997856 is about 271.4320617939.

The spelling of 19997856 in words is "nineteen million, nine hundred ninety-seven thousand, eight hundred fifty-six".