19809720 has 144 divisors (see below), whose sum is σ = 74959560. Its totient is φ = 4523904.

The previous prime is 19809679. The next prime is 19809721. The reversal of 19809720 is 2790891.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19809721) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 17079 + ... + 18201.

Almost surely, 2^19809720 is an apocalyptic number.

19809720 is a gapful number since it is divisible by the number (10) 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 19809720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37479780).

19809720 is an abundant number, since it is smaller than the sum of its proper divisors (55149840).

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

19809720 is a wasteful number, since it uses less digits than its factorization.

19809720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1154 (or 1140 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

The square root of 19809720 is about 4450.8111620243. The cubic root of 19809720 is about 270.5781848448.

The spelling of 19809720 in words is "nineteen million, eight hundred nine thousand, seven hundred twenty".