21641280 has 56 divisors (see below), whose sum is σ = 68714112. Its totient is φ = 5770752.

The previous prime is 21641267. The next prime is 21641281. The reversal of 21641280 is 8214612.

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 21641280.

It is not an unprimeable number, because it can be changed into a prime (21641281) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10312 + ... + 12231.

Almost surely, 2^21641280 is an apocalyptic number.

21641280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21641280 is an abundant number, since it is smaller than the sum of its proper divisors (47072832).

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

21641280 is a wasteful number, since it uses less digits than its factorization.

21641280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22563 (or 22553 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21641280 is about 4652.0189165566. The cubic root of 21641280 is about 278.6726289586.

Adding to 21641280 its reverse (8214612), we get a palindrome (29855892).

The spelling of 21641280 in words is "twenty-one million, six hundred forty-one thousand, two hundred eighty".