20521320 has 128 divisors (see below), whose sum is σ = 65197440. Its totient is φ = 5160960.

The previous prime is 20521309. The next prime is 20521331. The reversal of 20521320 is 2312502.

It is an interprime number because it is at equal distance from previous prime (20521309) and next prime (20521331).

It is a super-2 number, since 2×20521320² = 842249149084800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 20521320.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 211512 + ... + 211608.

It is an arithmetic number, because the mean of its divisors is an integer number (509355).

Almost surely, 2^20521320 is an apocalyptic number.

20521320 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 20521320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32598720).

20521320 is an abundant number, since it is smaller than the sum of its proper divisors (44676120).

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

20521320 is a wasteful number, since it uses less digits than its factorization.

20521320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195 (or 191 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 15.

The square root of 20521320 is about 4530.0463573787. The cubic root of 20521320 is about 273.7800283984.

Adding to 20521320 its reverse (2312502), we get a palindrome (22833822).

The spelling of 20521320 in words is "twenty million, five hundred twenty-one thousand, three hundred twenty".