20840040 has 192 divisors, whose sum is σ = 75151440. Its totient is φ = 4976640.

The previous prime is 20840033. The next prime is 20840041. The reversal of 20840040 is 4004802.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 1285956 + 19554084 = 1134^2 + 4422^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 20839995 and 20840022.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20840041) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 285444 + ... + 285516.

Almost surely, 2^20840040 is an apocalyptic number.

20840040 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 20840040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37575720).

20840040 is an abundant number, since it is smaller than the sum of its proper divisors (54311400).

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

20840040 is a wasteful number, since it uses less digits than its factorization.

20840040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164 (or 157 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 20840040 is about 4565.0892652828. The cubic root of 20840040 is about 275.1901274739.

Adding to 20840040 its reverse (4004802), we get a palindrome (24844842).

The spelling of 20840040 in words is "twenty million, eight hundred forty thousand, forty".