21825815 has 8 divisors (see below), whose sum is σ = 28572048. Its totient is φ = 15873280.

The previous prime is 21825757. The next prime is 21825887. The reversal of 21825815 is 51852812.

It is a happy number.

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

It is not a de Polignac number, because 21825815 - 2⁶ = 21825751 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 198362 + ... + 198471.

It is an arithmetic number, because the mean of its divisors is an integer number (3571506).

Almost surely, 2^21825815 is an apocalyptic number.

21825815 is a deficient number, since it is larger than the sum of its proper divisors (6746233).

21825815 is a wasteful number, since it uses less digits than its factorization.

21825815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 396849.

The product of its digits is 6400, while the sum is 32.

The square root of 21825815 is about 4671.8106768147. The cubic root of 21825815 is about 279.4624678787.

It can be divided in two parts, 2182 and 5815, that added together give a palindrome (7997).

The spelling of 21825815 in words is "twenty-one million, eight hundred twenty-five thousand, eight hundred fifteen".