21011881 has 8 divisors (see below), whose sum is σ = 24270624. Its totient is φ = 17977920.

The previous prime is 21011873. The next prime is 21011917. The reversal of 21011881 is 18811012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21011881 - 2³ = 21011873 is a prime.

It is a super-2 number, since 2×21011881² = 882998286316322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21011981) 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 7 ways as a sum of consecutive naturals, for example, 55995 + ... + 56368.

It is an arithmetic number, because the mean of its divisors is an integer number (3033828).

Almost surely, 2^21011881 is an apocalyptic number.

It is an amenable number.

21011881 is a deficient number, since it is larger than the sum of its proper divisors (3258743).

21011881 is a wasteful number, since it uses less digits than its factorization.

21011881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112391.

The product of its (nonzero) digits is 128, while the sum is 22.

The square root of 21011881 is about 4583.8718350320. The cubic root of 21011881 is about 275.9444376356.

Adding to 21011881 its reverse (18811012), we get a palindrome (39822893).

The spelling of 21011881 in words is "twenty-one million, eleven thousand, eight hundred eighty-one".