21307855 has 8 divisors (see below), whose sum is σ = 26052192. Its totient is φ = 16724448.

The previous prime is 21307841. The next prime is 21307859. The reversal of 21307855 is 55870312.

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

It is a cyclic number.

It is not a de Polignac number, because 21307855 - 2¹⁵ = 21275087 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21307859) 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, 39939 + ... + 40468.

It is an arithmetic number, because the mean of its divisors is an integer number (3256524).

Almost surely, 2^21307855 is an apocalyptic number.

21307855 is a deficient number, since it is larger than the sum of its proper divisors (4744337).

21307855 is an equidigital number, since it uses as much as digits as its factorization.

21307855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80465.

The product of its (nonzero) digits is 8400, while the sum is 31.

The square root of 21307855 is about 4616.0432190351. The cubic root of 21307855 is about 277.2340551963.

The spelling of 21307855 in words is "twenty-one million, three hundred seven thousand, eight hundred fifty-five".