21053520 has 210 divisors, whose sum is σ = 77456538. Its totient is φ = 5318784.

The previous prime is 21053503. The next prime is 21053521. The reversal of 21053520 is 2535012.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 16842816 + 4210704 = 4104^2 + 2052^2 .

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

It is a zygodrome in base 4.

It is a junction number, because it is equal to n+sod(n) for n = 21053493 and 21053502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21053521) by changing a digit.

It is a polite number, since it can be written in 41 ways as a sum of consecutive naturals, for example, 1108071 + ... + 1108089.

Almost surely, 2^21053520 is an apocalyptic number.

21053520 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 21053520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38728269).

21053520 is an abundant number, since it is smaller than the sum of its proper divisors (56403018).

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

21053520 is an equidigital number, since it uses as much as digits as its factorization.

21053520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69 (or 29 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 18.

The square root of 21053520 is about 4588.4114898296. The cubic root of 21053520 is about 276.1265959882.

Adding to 21053520 its reverse (2535012), we get a palindrome (23588532).

It can be divided in two parts, 2105 and 3520, that added together give a square (5625 = 75²).

The spelling of 21053520 in words is "twenty-one million, fifty-three thousand, five hundred twenty".