21973865 has 4 divisors (see below), whose sum is σ = 26368644. Its totient is φ = 17579088.

The previous prime is 21973849. The next prime is 21973871. The reversal of 21973865 is 56837912.

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 15808576 + 6165289 = 3976^2 + 2483^2 .

It is a cyclic number.

It is not a de Polignac number, because 21973865 - 2⁴ = 21973849 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, 2197382 + ... + 2197391.

It is an arithmetic number, because the mean of its divisors is an integer number (6592161).

Almost surely, 2^21973865 is an apocalyptic number.

It is an amenable number.

21973865 is a deficient number, since it is larger than the sum of its proper divisors (4394779).

21973865 is an equidigital number, since it uses as much as digits as its factorization.

21973865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4394778.

The product of its digits is 90720, while the sum is 41.

The square root of 21973865 is about 4687.6289315602. The cubic root of 21973865 is about 280.0929325874.

The spelling of 21973865 in words is "twenty-one million, nine hundred seventy-three thousand, eight hundred sixty-five".