21350520 has 128 divisors (see below), whose sum is σ = 72705600. Its totient is φ = 5571072.

The previous prime is 21350501. The next prime is 21350533. The reversal of 21350520 is 2505312.

It is a happy number.

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 = 21350493 and 21350502.

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 57054 + ... + 57426.

Almost surely, 2^21350520 is an apocalyptic number.

21350520 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 21350520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36352800).

21350520 is an abundant number, since it is smaller than the sum of its proper divisors (51355080).

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

21350520 is a wasteful number, since it uses less digits than its factorization.

21350520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 446 (or 436 counting only the distinct ones).

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

The square root of 21350520 is about 4620.6622901917. The cubic root of 21350520 is about 277.4189683055.

Adding to 21350520 its reverse (2505312), we get a palindrome (23855832).

The spelling of 21350520 in words is "twenty-one million, three hundred fifty thousand, five hundred twenty".