21859555 has 4 divisors (see below), whose sum is σ = 26231472. Its totient is φ = 17487640.

The previous prime is 21859549. The next prime is 21859561. The reversal of 21859555 is 55595812.

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 (21859549) and next prime (21859561).

It is not a de Polignac number, because 21859555 - 2³ = 21859547 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2185951 + ... + 2185960.

It is an arithmetic number, because the mean of its divisors is an integer number (6557868).

Almost surely, 2^21859555 is an apocalyptic number.

21859555 is a deficient number, since it is larger than the sum of its proper divisors (4371917).

21859555 is an equidigital number, since it uses as much as digits as its factorization.

21859555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4371916.

The product of its digits is 90000, while the sum is 40.

The square root of 21859555 is about 4675.4203019622. The cubic root of 21859555 is about 279.6063984965.

The spelling of 21859555 in words is "twenty-one million, eight hundred fifty-nine thousand, five hundred fifty-five".