21103881 has 4 divisors (see below), whose sum is σ = 28138512. Its totient is φ = 14069252.

The previous prime is 21103879. The next prime is 21103883. The reversal of 21103881 is 18830112.

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 an interprime number because it is at equal distance from previous prime (21103879) and next prime (21103883).

It is a cyclic number.

It is not a de Polignac number, because 21103881 - 2¹ = 21103879 is a prime.

It is a super-2 number, since 2×21103881² = 890747586524322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21103883) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3517311 + ... + 3517316.

It is an arithmetic number, because the mean of its divisors is an integer number (7034628).

Almost surely, 2^21103881 is an apocalyptic number.

It is an amenable number.

21103881 is a deficient number, since it is larger than the sum of its proper divisors (7034631).

21103881 is an equidigital number, since it uses as much as digits as its factorization.

21103881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7034630.

The product of its (nonzero) digits is 384, while the sum is 24.

The square root of 21103881 is about 4593.8960589025. The cubic root of 21103881 is about 276.3465898937.

Adding to 21103881 its reverse (18830112), we get a palindrome (39933993).

The spelling of 21103881 in words is "twenty-one million, one hundred three thousand, eight hundred eighty-one".