21259655 has 4 divisors (see below), whose sum is σ = 25511592. Its totient is φ = 17007720.

The previous prime is 21259627. The next prime is 21259657. The reversal of 21259655 is 55695212.

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

It is not a de Polignac number, because 21259655 - 2¹⁸ = 20997511 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 (21259657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2125961 + ... + 2125970.

It is an arithmetic number, because the mean of its divisors is an integer number (6377898).

Almost surely, 2^21259655 is an apocalyptic number.

21259655 is a deficient number, since it is larger than the sum of its proper divisors (4251937).

21259655 is an equidigital number, since it uses as much as digits as its factorization.

21259655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4251936.

The product of its digits is 27000, while the sum is 35.

The square root of 21259655 is about 4610.8193415054. The cubic root of 21259655 is about 277.0248558198.

The spelling of 21259655 in words is "twenty-one million, two hundred fifty-nine thousand, six hundred fifty-five".