21852821 has 4 divisors (see below), whose sum is σ = 22116192. Its totient is φ = 21589452.

The previous prime is 21852797. The next prime is 21852827. The reversal of 21852821 is 12825812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21852821 - 2²² = 17658517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21852827) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 131561 + ... + 131726.

It is an arithmetic number, because the mean of its divisors is an integer number (5529048).

Almost surely, 2^21852821 is an apocalyptic number.

It is an amenable number.

21852821 is a deficient number, since it is larger than the sum of its proper divisors (263371).

21852821 is an equidigital number, since it uses as much as digits as its factorization.

21852821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 263370.

The product of its digits is 2560, while the sum is 29.

The square root of 21852821 is about 4674.7000973324. The cubic root of 21852821 is about 279.5776839311.

The spelling of 21852821 in words is "twenty-one million, eight hundred fifty-two thousand, eight hundred twenty-one".