20787840 has 160 divisors (see below), whose sum is σ = 74422260. Its totient is φ = 5529600.

The previous prime is 20787839. The next prime is 20787857. The reversal of 20787840 is 4878702.

It can be written as a sum of positive squares in 2 ways, for example, as 19289664 + 1498176 = 4392^2 + 1224^2 .

It is a tau number, because it is divible by the number of its divisors (160).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

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

It is a junction number, because it is equal to n+sod(n) for n = 20787795 and 20787804.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 51640 + ... + 52040.

Almost surely, 2^20787840 is an apocalyptic number.

20787840 is a gapful number since it is divisible by the number (20) 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 20787840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37211130).

20787840 is an abundant number, since it is smaller than the sum of its proper divisors (53634420).

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

20787840 is an equidigital number, since it uses as much as digits as its factorization.

20787840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 432 (or 411 counting only the distinct ones).

The product of its (nonzero) digits is 25088, while the sum is 36.

The square root of 20787840 is about 4559.3683773084. The cubic root of 20787840 is about 274.9601705401.

The spelling of 20787840 in words is "twenty million, seven hundred eighty-seven thousand, eight hundred forty".