21815522 has 8 divisors (see below), whose sum is σ = 34648236. Its totient is φ = 10266112.

The previous prime is 21815483. The next prime is 21815527. The reversal of 21815522 is 22551812.

It can be written as a sum of positive squares in 2 ways, for example, as 21724921 + 90601 = 4661^2 + 301^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-3 number, since 3×21815522³ (a number of 23 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21815491 and 21815500.

It is not an unprimeable number, because it can be changed into a prime (21815527) 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 3 ways as a sum of consecutive naturals, for example, 320783 + ... + 320850.

Almost surely, 2^21815522 is an apocalyptic number.

21815522 is a deficient number, since it is larger than the sum of its proper divisors (12832714).

21815522 is a wasteful number, since it uses less digits than its factorization.

21815522 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 641652.

The product of its digits is 1600, while the sum is 26.

The square root of 21815522 is about 4670.7089397649. The cubic root of 21815522 is about 279.4185297029.

The spelling of 21815522 in words is "twenty-one million, eight hundred fifteen thousand, five hundred twenty-two".