21753820 has 48 divisors (see below), whose sum is σ = 50684256. Its totient is φ = 7776000.

The previous prime is 21753793. The next prime is 21753827. The reversal of 21753820 is 2835712.

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21753827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12610 + ... + 14230.

It is an arithmetic number, because the mean of its divisors is an integer number (1055922).

Almost surely, 2^21753820 is an apocalyptic number.

21753820 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 21753820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25342128).

21753820 is an abundant number, since it is smaller than the sum of its proper divisors (28930436).

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

21753820 is a wasteful number, since it uses less digits than its factorization.

21753820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1702 (or 1700 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 21753820 is about 4664.0990555519. The cubic root of 21753820 is about 279.1548495283.

It can be divided in two parts, 2175 and 3820, that added together give a palindrome (5995).

The spelling of 21753820 in words is "twenty-one million, seven hundred fifty-three thousand, eight hundred twenty".