21232640 has 176 divisors, whose sum is σ = 61901280. Its totient is φ = 6881280.

The previous prime is 21232639. The next prime is 21232663. The reversal of 21232640 is 4623212.

It is a tau number, because it is divible by the number of its divisors (176).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a zygodrome in base 4.

It is a congruent number.

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, 732146 + ... + 732174.

Almost surely, 2^21232640 is an apocalyptic number.

21232640 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 21232640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30950640).

21232640 is an abundant number, since it is smaller than the sum of its proper divisors (40668640).

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

21232640 is a wasteful number, since it uses less digits than its factorization.

21232640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78 (or 60 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 21232640 is about 4607.8888875493. Note that the first 5 decimals coincide. The cubic root of 21232640 is about 276.9074660399.

Adding to 21232640 its reverse (4623212), we get a palindrome (25855852).

The spelling of 21232640 in words is "twenty-one million, two hundred thirty-two thousand, six hundred forty".