21871872 has 108 divisors (see below), whose sum is σ = 68874624. Its totient is φ = 6620160.

The previous prime is 21871849. The next prime is 21871903. The reversal of 21871872 is 27817812.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

Its product of digits (12544) is a multiple of the sum of its prime factors (896).

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 11 ways as a sum of consecutive naturals, for example, 24913 + ... + 25775.

It is an arithmetic number, because the mean of its divisors is an integer number (637728).

Almost surely, 2^21871872 is an apocalyptic number.

21871872 is a gapful number since it is divisible by the number (22) 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 21871872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34437312).

21871872 is an abundant number, since it is smaller than the sum of its proper divisors (47002752).

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

21871872 is a wasteful number, since it uses less digits than its factorization.

21871872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 896 (or 879 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 21871872 is about 4676.7373242465. The cubic root of 21871872 is about 279.6589043744.

The spelling of 21871872 in words is "twenty-one million, eight hundred seventy-one thousand, eight hundred seventy-two".