21755881 has 4 divisors (see below), whose sum is σ = 24863872. Its totient is φ = 18647892.

The previous prime is 21755873. The next prime is 21755897. The reversal of 21755881 is 18855712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21755881 - 2³ = 21755873 is a prime.

It is a super-2 number, since 2×21755881² = 946636716172322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21755881.

It is not an unprimeable number, because it can be changed into a prime (21755381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1553985 + ... + 1553998.

It is an arithmetic number, because the mean of its divisors is an integer number (6215968).

Almost surely, 2^21755881 is an apocalyptic number.

It is an amenable number.

21755881 is a deficient number, since it is larger than the sum of its proper divisors (3107991).

21755881 is an equidigital number, since it uses as much as digits as its factorization.

21755881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3107990.

The product of its digits is 22400, while the sum is 37.

The square root of 21755881 is about 4664.3199933109. The cubic root of 21755881 is about 279.1636651443.

The spelling of 21755881 in words is "twenty-one million, seven hundred fifty-five thousand, eight hundred eighty-one".