21533215 has 16 divisors (see below), whose sum is σ = 28460160. Its totient is φ = 15509920.

The previous prime is 21533207. The next prime is 21533219. The reversal of 21533215 is 51233512.

It is not a de Polignac number, because 21533215 - 2³ = 21533207 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21533219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4056 + ... + 7714.

It is an arithmetic number, because the mean of its divisors is an integer number (1778760).

Almost surely, 2^21533215 is an apocalyptic number.

21533215 is a deficient number, since it is larger than the sum of its proper divisors (6926945).

21533215 is a wasteful number, since it uses less digits than its factorization.

21533215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3782.

The product of its digits is 900, while the sum is 22.

The square root of 21533215 is about 4640.3895310631. The cubic root of 21533215 is about 278.2080072904.

Adding to 21533215 its reverse (51233512), we get a palindrome (72766727).

The spelling of 21533215 in words is "twenty-one million, five hundred thirty-three thousand, two hundred fifteen".