21513228 has 48 divisors (see below), whose sum is σ = 57988224. Its totient is φ = 6135040.

The previous prime is 21513227. The next prime is 21513241. The reversal of 21513228 is 82231512.

It is a junction number, because it is equal to n+sod(n) for n = 21513198 and 21513207.

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

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2550 + ... + 7037.

It is an arithmetic number, because the mean of its divisors is an integer number (1208088).

Almost surely, 2^21513228 is an apocalyptic number.

It is an amenable number.

21513228 is an abundant number, since it is smaller than the sum of its proper divisors (36474996).

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

21513228 is a wasteful number, since it uses less digits than its factorization.

21513228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9622 (or 9620 counting only the distinct ones).

The product of its digits is 960, while the sum is 24.

The square root of 21513228 is about 4638.2354403372. The cubic root of 21513228 is about 278.1219036477.

The spelling of 21513228 in words is "twenty-one million, five hundred thirteen thousand, two hundred twenty-eight".