21840500 has 108 divisors (see below), whose sum is σ = 55334916. Its totient is φ = 7524000.

The previous prime is 21840499. The next prime is 21840521. The reversal of 21840500 is 504812.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in 2 ways, for example, as 698896 + 21141604 = 836^2 + 4598^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

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 35 ways as a sum of consecutive naturals, for example, 1149491 + ... + 1149509.

Almost surely, 2^21840500 is an apocalyptic number.

21840500 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 21840500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27667458).

21840500 is an abundant number, since it is smaller than the sum of its proper divisors (33494416).

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

21840500 is a wasteful number, since it uses less digits than its factorization.

21840500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79 (or 37 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 21840500 is about 4673.3820729746. The cubic root of 21840500 is about 279.5251304685.

Multiplying 21840500 by its sum of digits (20), we get a square (436810000 = 20900²).

21840500 divided by its sum of digits (20) gives a square (1092025 = 1045²).

Multiplying 21840500 by its product of nonzero digits (320), we get a square (6988960000 = 83600²).

The spelling of 21840500 in words is "twenty-one million, eight hundred forty thousand, five hundred".