21873540 has 96 divisors (see below), whose sum is σ = 68302080. Its totient is φ = 5193216.

The previous prime is 21873539. The next prime is 21873589. The reversal of 21873540 is 4537812.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21873498 and 21873507.

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 31 ways as a sum of consecutive naturals, for example, 22137 + ... + 23103.

It is an arithmetic number, because the mean of its divisors is an integer number (711480).

Almost surely, 2^21873540 is an apocalyptic number.

21873540 is a gapful number since it is divisible by the number (20) 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 21873540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34151040).

21873540 is an abundant number, since it is smaller than the sum of its proper divisors (46428540).

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

21873540 is a wasteful number, since it uses less digits than its factorization.

21873540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1021 (or 1019 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 21873540 is about 4676.9156502977. The cubic root of 21873540 is about 279.6660133406. Note that the first 3 decimals are identical.

The spelling of 21873540 in words is "twenty-one million, eight hundred seventy-three thousand, five hundred forty".