21513220 has 24 divisors (see below), whose sum is σ = 45267264. Its totient is φ = 8588256.

The previous prime is 21513209. The next prime is 21513227. The reversal of 21513220 is 2231512.

It is a junction number, because it is equal to n+sod(n) for n = 21513194 and 21513203.

It is not an unprimeable number, because it can be changed into a prime (21513227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15807 + ... + 17113.

It is an arithmetic number, because the mean of its divisors is an integer number (1886136).

Almost surely, 2^21513220 is an apocalyptic number.

21513220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21513220 is an abundant number, since it is smaller than the sum of its proper divisors (23754044).

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

21513220 is a wasteful number, since it uses less digits than its factorization.

21513220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2139 (or 2137 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21513220 is about 4638.2345779402. The cubic root of 21513220 is about 278.1218691732.

Adding to 21513220 its reverse (2231512), we get a palindrome (23744732).

The spelling of 21513220 in words is "twenty-one million, five hundred thirteen thousand, two hundred twenty".