21755887 has 4 divisors (see below), whose sum is σ = 22506120. Its totient is φ = 21005656.

The previous prime is 21755873. The next prime is 21755897. The reversal of 21755887 is 78855712.

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

It is a cyclic number.

It is not a de Polignac number, because 21755887 - 2¹¹ = 21753839 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 (21755897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 375073 + ... + 375130.

It is an arithmetic number, because the mean of its divisors is an integer number (5626530).

Almost surely, 2^21755887 is an apocalyptic number.

21755887 is a deficient number, since it is larger than the sum of its proper divisors (750233).

21755887 is an equidigital number, since it uses as much as digits as its factorization.

21755887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 750232.

The product of its digits is 156800, while the sum is 43.

The square root of 21755887 is about 4664.3206364914. The cubic root of 21755887 is about 279.1636908076.

The spelling of 21755887 in words is "twenty-one million, seven hundred fifty-five thousand, eight hundred eighty-seven".