20505040 has 20 divisors (see below), whose sum is σ = 47674404. Its totient is φ = 8201984.

The previous prime is 20505031. The next prime is 20505041. The reversal of 20505040 is 4050502.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5419584 + 15085456 = 2328^2 + 3884^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20505041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 128077 + ... + 128236.

Almost surely, 2^20505040 is an apocalyptic number.

20505040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20505040 is an abundant number, since it is smaller than the sum of its proper divisors (27169364).

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

20505040 is a wasteful number, since it uses less digits than its factorization.

20505040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256326 (or 256320 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 16.

The square root of 20505040 is about 4528.2491097553. The cubic root of 20505040 is about 273.7076107367.

Adding to 20505040 its reverse (4050502), we get a palindrome (24555542).

The spelling of 20505040 in words is "twenty million, five hundred five thousand, forty".