21364865 has 4 divisors (see below), whose sum is σ = 25637844. Its totient is φ = 17091888.

The previous prime is 21364853. The next prime is 21364877. The reversal of 21364865 is 56846312.

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

It is an interprime number because it is at equal distance from previous prime (21364853) and next prime (21364877).

It can be written as a sum of positive squares in 2 ways, for example, as 16908544 + 4456321 = 4112^2 + 2111^2 .

It is a cyclic number.

It is not a de Polignac number, because 21364865 - 2¹⁶ = 21299329 is a prime.

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, 2136482 + ... + 2136491.

It is an arithmetic number, because the mean of its divisors is an integer number (6409461).

Almost surely, 2^21364865 is an apocalyptic number.

It is an amenable number.

21364865 is a deficient number, since it is larger than the sum of its proper divisors (4272979).

21364865 is an equidigital number, since it uses as much as digits as its factorization.

21364865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4272978.

The product of its digits is 34560, while the sum is 35.

The square root of 21364865 is about 4622.2142962005. The cubic root of 21364865 is about 277.4810852027.

The spelling of 21364865 in words is "twenty-one million, three hundred sixty-four thousand, eight hundred sixty-five".