21520330 has 16 divisors (see below), whose sum is σ = 41716584. Its totient is φ = 7945920.

The previous prime is 21520307. The next prime is 21520361. The reversal of 21520330 is 3302512.

It can be written as a sum of positive squares in 4 ways, for example, as 7733961 + 13786369 = 2781^2 + 3713^2 .

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, 82641 + ... + 82900.

Almost surely, 2^21520330 is an apocalyptic number.

21520330 is a deficient number, since it is larger than the sum of its proper divisors (20196254).

21520330 is a wasteful number, since it uses less digits than its factorization.

21520330 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165561.

The product of its (nonzero) digits is 180, while the sum is 16.

The square root of 21520330 is about 4639.0009700365. Note that the first 3 decimals coincide. The cubic root of 21520330 is about 278.1525050440.

Adding to 21520330 its reverse (3302512), we get a palindrome (24822842).

The spelling of 21520330 in words is "twenty-one million, five hundred twenty thousand, three hundred thirty".