21936881 has 4 divisors (see below), whose sum is σ = 22296564. Its totient is φ = 21577200.

The previous prime is 21936869. The next prime is 21936883. The reversal of 21936881 is 18863912.

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

It can be written as a sum of positive squares in 2 ways, for example, as 4431025 + 17505856 = 2105^2 + 4184^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21936881 is a prime.

It is a super-2 number, since 2×21936881² = 962453496016322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21936883) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 179750 + ... + 179871.

It is an arithmetic number, because the mean of its divisors is an integer number (5574141).

Almost surely, 2^21936881 is an apocalyptic number.

It is an amenable number.

21936881 is a deficient number, since it is larger than the sum of its proper divisors (359683).

21936881 is an equidigital number, since it uses as much as digits as its factorization.

21936881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 359682.

The product of its digits is 20736, while the sum is 38.

The square root of 21936881 is about 4683.6824187812. The cubic root of 21936881 is about 279.9357037742.

The spelling of 21936881 in words is "twenty-one million, nine hundred thirty-six thousand, eight hundred eighty-one".