19890816 has 128 divisors (see below), whose sum is σ = 61248960. Its totient is φ = 5652480.

The previous prime is 19890797. The next prime is 19890817. The reversal of 19890816 is 61809891.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×19890816² = 791289122291712, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (19890817) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 71670 + ... + 71946.

Almost surely, 2^19890816 is an apocalyptic number.

19890816 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 19890816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30624480).

19890816 is an abundant number, since it is smaller than the sum of its proper divisors (41358144).

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

19890816 is a wasteful number, since it uses less digits than its factorization.

19890816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322 (or 310 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 42.

The square root of 19890816 is about 4459.9121067573. The cubic root of 19890816 is about 270.9469084414.

It can be divided in two parts, 19890 and 816, that added together give a triangular number (20706 = T₂₀₃).

The spelling of 19890816 in words is "nineteen million, eight hundred ninety thousand, eight hundred sixteen".