21231084 has 48 divisors (see below), whose sum is σ = 56947968. Its totient is φ = 6030528.

The previous prime is 21231029. The next prime is 21231107. The reversal of 21231084 is 48013212.

It is a super-4 number, since 4×21231084⁴ (a number of 30 digits) contains 4444 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a self number, because there is not a number n which added to its sum of digits gives 21231084.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15907 + ... + 17189.

It is an arithmetic number, because the mean of its divisors is an integer number (1186416).

Almost surely, 2^21231084 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21231084, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28473984).

21231084 is an abundant number, since it is smaller than the sum of its proper divisors (35716884).

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

21231084 is a wasteful number, since it uses less digits than its factorization.

21231084 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1494 (or 1492 counting only the distinct ones).

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

The square root of 21231084 is about 4607.7200435790. The cubic root of 21231084 is about 276.9007016347.

Adding to 21231084 its reverse (48013212), we get a palindrome (69244296).

The spelling of 21231084 in words is "twenty-one million, two hundred thirty-one thousand, eighty-four".