20511220 has 12 divisors (see below), whose sum is σ = 43073604. Its totient is φ = 8204480.

The previous prime is 20511217. The next prime is 20511221. The reversal of 20511220 is 2211502.

It can be written as a sum of positive squares in 2 ways, for example, as 5934096 + 14577124 = 2436^2 + 3818^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 20511220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20511221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 512761 + ... + 512800.

It is an arithmetic number, because the mean of its divisors is an integer number (3589467).

Almost surely, 2^20511220 is an apocalyptic number.

20511220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20511220 is an abundant number, since it is smaller than the sum of its proper divisors (22562384).

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

20511220 is a wasteful number, since it uses less digits than its factorization.

20511220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1025570 (or 1025568 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 20511220 is about 4528.9314413005. The cubic root of 20511220 is about 273.7351054913.

Adding to 20511220 its reverse (2211502), we get a palindrome (22722722).

The spelling of 20511220 in words is "twenty million, five hundred eleven thousand, two hundred twenty".