21255745 has 8 divisors (see below), whose sum is σ = 29150784. Its totient is φ = 14575344.

The previous prime is 21255743. The next prime is 21255757. The reversal of 21255745 is 54755212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21255745 - 2¹ = 21255743 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21255743) 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, 303619 + ... + 303688.

It is an arithmetic number, because the mean of its divisors is an integer number (3643848).

Almost surely, 2^21255745 is an apocalyptic number.

It is an amenable number.

21255745 is a deficient number, since it is larger than the sum of its proper divisors (7895039).

21255745 is an equidigital number, since it uses as much as digits as its factorization.

21255745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 607319.

The product of its digits is 14000, while the sum is 31.

The square root of 21255745 is about 4610.3953192758. The cubic root of 21255745 is about 277.0078716370.

The spelling of 21255745 in words is "twenty-one million, two hundred fifty-five thousand, seven hundred forty-five".