20615220 has 72 divisors (see below), whose sum is σ = 66221064. Its totient is φ = 5173248.

The previous prime is 20615213. The next prime is 20615233. The reversal of 20615220 is 2251602.

It can be written as a sum of positive squares in 4 ways, for example, as 4309776 + 16305444 = 2076^2 + 4038^2 .

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 = 20615193 and 20615202.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 309 + ... + 6428.

It is an arithmetic number, because the mean of its divisors is an integer number (919737).

Almost surely, 2^20615220 is an apocalyptic number.

20615220 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 20615220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33110532).

20615220 is an abundant number, since it is smaller than the sum of its proper divisors (45605844).

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

20615220 is a wasteful number, since it uses less digits than its factorization.

20615220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6769 (or 6764 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 20615220 is about 4540.3986609107. The cubic root of 20615220 is about 274.1969741760.

Adding to 20615220 its reverse (2251602), we get a palindrome (22866822).

The spelling of 20615220 in words is "twenty million, six hundred fifteen thousand, two hundred twenty".