21853421 has 8 divisors (see below), whose sum is σ = 22679160. Its totient is φ = 21040128.

The previous prime is 21853399. The next prime is 21853487. The reversal of 21853421 is 12435812.

It can be written as a sum of positive squares in 4 ways, for example, as 4120900 + 17732521 = 2030^2 + 4211^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21853421 - 2¹⁴ = 21837037 is a prime.

It is a super-5 number, since 5×21853421⁵ (a number of 38 digits) contains 55555 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21853121) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 545 + ... + 6633.

It is an arithmetic number, because the mean of its divisors is an integer number (2834895).

Almost surely, 2^21853421 is an apocalyptic number.

It is an amenable number.

21853421 is a deficient number, since it is larger than the sum of its proper divisors (825739).

21853421 is an equidigital number, since it uses as much as digits as its factorization.

21853421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6223.

The product of its digits is 1920, while the sum is 26.

The square root of 21853421 is about 4674.7642721318. The cubic root of 21853421 is about 279.5802426408.

The spelling of 21853421 in words is "twenty-one million, eight hundred fifty-three thousand, four hundred twenty-one".