21871824 has 40 divisors (see below), whose sum is σ = 60850272. Its totient is φ = 6729600.

The previous prime is 21871807. The next prime is 21871841. The reversal of 21871824 is 42817812.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21871807) and next prime (21871841).

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 16902 + ... + 18149.

Almost surely, 2^21871824 is an apocalyptic number.

21871824 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21871824 is an abundant number, since it is smaller than the sum of its proper divisors (38978448).

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

21871824 is a wasteful number, since it uses less digits than its factorization.

21871824 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35075 (or 35069 counting only the distinct ones).

The product of its digits is 7168, while the sum is 33.

The square root of 21871824 is about 4676.7321924609. The cubic root of 21871824 is about 279.6586997945.

It can be divided in two parts, 2187182 and 4, that added together give a triangular number (2187186 = T₂₀₉₁).

The spelling of 21871824 in words is "twenty-one million, eight hundred seventy-one thousand, eight hundred twenty-four".