21839220 has 240 divisors, whose sum is σ = 79401168. Its totient is φ = 4976640.

The previous prime is 21839219. The next prime is 21839231. The reversal of 21839220 is 2293812.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 3640464 + 18198756 = 1908^2 + 4266^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 357990 + ... + 358050.

Almost surely, 2^21839220 is an apocalyptic number.

21839220 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 21839220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39700584).

21839220 is an abundant number, since it is smaller than the sum of its proper divisors (57561948).

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

21839220 is a wasteful number, since it uses less digits than its factorization.

21839220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112 (or 101 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21839220 is about 4673.2451251780. The cubic root of 21839220 is about 279.5196696784.

The spelling of 21839220 in words is "twenty-one million, eight hundred thirty-nine thousand, two hundred twenty".