21256465 has 4 divisors (see below), whose sum is σ = 25507764. Its totient is φ = 17005168.

The previous prime is 21256457. The next prime is 21256471. The reversal of 21256465 is 56465212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6990736 + 14265729 = 2644^2 + 3777^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256465 - 2³ = 21256457 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2125642 + ... + 2125651.

It is an arithmetic number, because the mean of its divisors is an integer number (6376941).

Almost surely, 2^21256465 is an apocalyptic number.

It is an amenable number.

21256465 is a deficient number, since it is larger than the sum of its proper divisors (4251299).

21256465 is an equidigital number, since it uses as much as digits as its factorization.

21256465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4251298.

The product of its digits is 14400, while the sum is 31.

The square root of 21256465 is about 4610.4734030249. The cubic root of 21256465 is about 277.0109993156.

The spelling of 21256465 in words is "twenty-one million, two hundred fifty-six thousand, four hundred sixty-five".