21026865 has 8 divisors (see below), whose sum is σ = 33643008. Its totient is φ = 11214320.

The previous prime is 21026861. The next prime is 21026867. The reversal of 21026865 is 56862012.

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

It is not a de Polignac number, because 21026865 - 2² = 21026861 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21026861) 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, 700881 + ... + 700910.

It is an arithmetic number, because the mean of its divisors is an integer number (4205376).

Almost surely, 2^21026865 is an apocalyptic number.

It is an amenable number.

21026865 is a deficient number, since it is larger than the sum of its proper divisors (12616143).

21026865 is a wasteful number, since it uses less digits than its factorization.

21026865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1401799.

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 21026865 is about 4585.5059699012. The cubic root of 21026865 is about 276.0100159146.

Adding to 21026865 its reverse (56862012), we get a palindrome (77888877).

The spelling of 21026865 in words is "twenty-one million, twenty-six thousand, eight hundred sixty-five".