21072480 has 192 divisors, whose sum is σ = 78236928. Its totient is φ = 4700160.

The previous prime is 21072449. The next prime is 21072481. The reversal of 21072480 is 8427012.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21072480.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21072481) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 68487 + ... + 68793.

It is an arithmetic number, because the mean of its divisors is an integer number (407484).

Almost surely, 2^21072480 is an apocalyptic number.

21072480 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 21072480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39118464).

21072480 is an abundant number, since it is smaller than the sum of its proper divisors (57164448).

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

21072480 is a wasteful number, since it uses less digits than its factorization.

21072480 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 349 (or 341 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 21072480 is about 4590.4770993874. The cubic root of 21072480 is about 276.2094608244.

Adding to 21072480 its reverse (8427012), we get a palindrome (29499492).

The spelling of 21072480 in words is "twenty-one million, seventy-two thousand, four hundred eighty".