21280755 has 16 divisors (see below), whose sum is σ = 34320384. Its totient is φ = 11259360.

The previous prime is 21280747. The next prime is 21280757. The reversal of 21280755 is 55708212.

It is not a de Polignac number, because 21280755 - 2³ = 21280747 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21280757) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3681 + ... + 7490.

It is an arithmetic number, because the mean of its divisors is an integer number (2145024).

Almost surely, 2^21280755 is an apocalyptic number.

21280755 is a deficient number, since it is larger than the sum of its proper divisors (13039629).

21280755 is a wasteful number, since it uses less digits than its factorization.

21280755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11306.

The product of its (nonzero) digits is 5600, while the sum is 30.

The square root of 21280755 is about 4613.1068706459. The cubic root of 21280755 is about 277.1164736713.

Adding to 21280755 its reverse (55708212), we get a palindrome (76988967).

The spelling of 21280755 in words is "twenty-one million, two hundred eighty thousand, seven hundred fifty-five".