19779840 has 216 divisors, whose sum is σ = 73179288. Its totient is φ = 4915200.

The previous prime is 19779803. The next prime is 19779841. The reversal of 19779840 is 4897791.

It can be written as a sum of positive squares in 4 ways, for example, as 9437184 + 10342656 = 3072^2 + 3216^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (19779841) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 195790 + ... + 195890.

It is an arithmetic number, because the mean of its divisors is an integer number (338793).

Almost surely, 2^19779840 is an apocalyptic number.

19779840 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 19779840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36589644).

19779840 is an abundant number, since it is smaller than the sum of its proper divisors (53399448).

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

19779840 is a wasteful number, since it uses less digits than its factorization.

19779840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145 (or 128 counting only the distinct ones).

The product of its (nonzero) digits is 127008, while the sum is 45.

The square root of 19779840 is about 4447.4532038010. The cubic root of 19779840 is about 270.4420741457.

The spelling of 19779840 in words is "nineteen million, seven hundred seventy-nine thousand, eight hundred forty".