21556655 has 4 divisors (see below), whose sum is σ = 25867992. Its totient is φ = 17245320.

The previous prime is 21556649. The next prime is 21556673. The reversal of 21556655 is 55665512.

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

It is not a de Polignac number, because 21556655 - 2¹⁴ = 21540271 is a prime.

It is a Duffinian number.

It is a congruent 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, 2155661 + ... + 2155670.

It is an arithmetic number, because the mean of its divisors is an integer number (6466998).

Almost surely, 2^21556655 is an apocalyptic number.

21556655 is a deficient number, since it is larger than the sum of its proper divisors (4311337).

21556655 is an equidigital number, since it uses as much as digits as its factorization.

21556655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4311336.

The product of its digits is 45000, while the sum is 35.

The square root of 21556655 is about 4642.9144941513. The cubic root of 21556655 is about 278.3089185400.

The spelling of 21556655 in words is "twenty-one million, five hundred fifty-six thousand, six hundred fifty-five".