21831420 has 72 divisors (see below), whose sum is σ = 66222576. Its totient is φ = 5371392.

The previous prime is 21831419. The next prime is 21831431. The reversal of 21831420 is 2413812.

It is a super-2 number, since 2×21831420² = 953221798432800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9064 + ... + 11216.

It is an arithmetic number, because the mean of its divisors is an integer number (919758).

Almost surely, 2^21831420 is an apocalyptic number.

21831420 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 21831420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33111288).

21831420 is an abundant number, since it is smaller than the sum of its proper divisors (44391156).

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

21831420 is a wasteful number, since it uses less digits than its factorization.

21831420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2191 (or 2176 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21831420 is about 4672.4105127867. The cubic root of 21831420 is about 279.4863883762.

The spelling of 21831420 in words is "twenty-one million, eight hundred thirty-one thousand, four hundred twenty".