21207255 has 32 divisors (see below), whose sum is σ = 35665920. Its totient is φ = 10746240.

The previous prime is 21207239. The next prime is 21207259. The reversal of 21207255 is 55270212.

It is not a de Polignac number, because 21207255 - 2⁴ = 21207239 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21207259) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 27049 + ... + 27821.

It is an arithmetic number, because the mean of its divisors is an integer number (1114560).

Almost surely, 2^21207255 is an apocalyptic number.

21207255 is a deficient number, since it is larger than the sum of its proper divisors (14458665).

21207255 is a wasteful number, since it uses less digits than its factorization.

21207255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 871.

The product of its (nonzero) digits is 1400, while the sum is 24.

The square root of 21207255 is about 4605.1335485521. The cubic root of 21207255 is about 276.7970684129.

Adding to 21207255 its reverse (55270212), we get a palindrome (76477467).

The spelling of 21207255 in words is "twenty-one million, two hundred seven thousand, two hundred fifty-five".