21842940 has 96 divisors (see below), whose sum is σ = 70608384. Its totient is φ = 4942080.

The previous prime is 21842929. The next prime is 21842957. The reversal of 21842940 is 4924812.

It is a super-2 number, since 2×21842940² = 954228055687200, which contains 22 as substring.

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 = 21842898 and 21842907.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 54822 + ... + 55218.

It is an arithmetic number, because the mean of its divisors is an integer number (735504).

Almost surely, 2^21842940 is an apocalyptic number.

21842940 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 21842940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35304192).

21842940 is an abundant number, since it is smaller than the sum of its proper divisors (48765444).

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

21842940 is a wasteful number, since it uses less digits than its factorization.

21842940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 547 (or 545 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 21842940 is about 4673.6431185960. The cubic root of 21842940 is about 279.5355395086.

The spelling of 21842940 in words is "twenty-one million, eight hundred forty-two thousand, nine hundred forty".