21230640 has 80 divisors (see below), whose sum is σ = 73135200. Its totient is φ = 5660928.

The previous prime is 21230617. The next prime is 21230641. The reversal of 21230640 is 4603212.

It is a happy number.

21230640 is a `hidden beast` number, since 2 + 1 + 23 + 0 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21230641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2755 + ... + 7074.

It is an arithmetic number, because the mean of its divisors is an integer number (914190).

Almost surely, 2^21230640 is an apocalyptic number.

21230640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21230640 is an abundant number, since it is smaller than the sum of its proper divisors (51904560).

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

21230640 is a wasteful number, since it uses less digits than its factorization.

21230640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9851 (or 9839 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21230640 is about 4607.6718633167. The cubic root of 21230640 is about 276.8987713710.

Adding to 21230640 its reverse (4603212), we get a palindrome (25833852).

The spelling of 21230640 in words is "twenty-one million, two hundred thirty thousand, six hundred forty".