21513520 has 80 divisors (see below), whose sum is σ = 58621248. Its totient is φ = 7188480.

The previous prime is 21513511. The next prime is 21513523. The reversal of 21513520 is 2531512.

21513520 is a nontrivial binomial coefficient, being equal to C(6560, 2).

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513523) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22492 + ... + 23428.

Almost surely, 2^21513520 is an apocalyptic number.

21513520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21513520 is the 6559-th triangular number and also the 3280-th hexagonal number.

21513520 is the 2187-th centered nonagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21513520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29310624).

21513520 is an abundant number, since it is smaller than the sum of its proper divisors (37107728).

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

21513520 is a wasteful number, since it uses less digits than its factorization.

21513520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 998 (or 992 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21513520 is about 4638.2669177183. The cubic root of 21513520 is about 278.1231619624.

It can be divided in two parts, 2151 and 3520, that added together give a triangular number (5671 = T₁₀₆).

The spelling of 21513520 in words is "twenty-one million, five hundred thirteen thousand, five hundred twenty".