21313520 has 40 divisors (see below), whose sum is σ = 49791456. Its totient is φ = 8484608.

The previous prime is 21313493. The next prime is 21313531. The reversal of 21313520 is 2531312.

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×21313520² = 908532269580800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20534 + ... + 21546.

Almost surely, 2^21313520 is an apocalyptic number.

21313520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21313520 is an abundant number, since it is smaller than the sum of its proper divisors (28477936).

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

21313520 is a wasteful number, since it uses less digits than its factorization.

21313520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1289 (or 1283 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 21313520 is about 4616.6567990268. The cubic root of 21313520 is about 277.2586219075.

Adding to 21313520 its reverse (2531312), we get a palindrome (23844832).

The spelling of 21313520 in words is "twenty-one million, three hundred thirteen thousand, five hundred twenty".