21280000 has 180 divisors, whose sum is σ = 63854560. Its totient is φ = 6912000.

The previous prime is 21279959. The next prime is 21280001. The reversal of 21280000 is 8212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21280001) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1119991 + ... + 1120009.

Almost surely, 2^21280000 is an apocalyptic number.

21280000 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 21280000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31927280).

21280000 is an abundant number, since it is smaller than the sum of its proper divisors (42574560).

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

21280000 is an frugal number, since it uses more digits than its factorization.

21280000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62 (or 33 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21280000 is about 4613.0250378683. The cubic root of 21280000 is about 277.1131964472.

Adding to 21280000 its reverse (8212), we get a palindrome (21288212).

It can be divided in two parts, 2 and 1280000, that multiplied together give a 4-th power (2560000 = 40⁴).

The spelling of 21280000 in words is "twenty-one million, two hundred eighty thousand".