21851424 has 96 divisors (see below), whose sum is σ = 72858240. Its totient is φ = 6241536.

The previous prime is 21851419. The next prime is 21851441. The reversal of 21851424 is 42415812.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (27).

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 15 ways as a sum of consecutive naturals, for example, 4242 + ... + 7854.

It is an arithmetic number, because the mean of its divisors is an integer number (758940).

Almost surely, 2^21851424 is an apocalyptic number.

21851424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21851424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36429120).

21851424 is an abundant number, since it is smaller than the sum of its proper divisors (51006816).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21851424 is a wasteful number, since it uses less digits than its factorization.

21851424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3639 (or 3625 counting only the distinct ones).

The product of its digits is 2560, while the sum is 27.

The square root of 21851424 is about 4674.5506735942. The cubic root of 21851424 is about 279.5717262205.

The spelling of 21851424 in words is "twenty-one million, eight hundred fifty-one thousand, four hundred twenty-four".