21223681 has 8 divisors (see below), whose sum is σ = 22063104. Its totient is φ = 20398320.

The previous prime is 21223673. The next prime is 21223693. The reversal of 21223681 is 18632212.

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 21223681 - 2³ = 21223673 is a prime.

It is a super-2 number, since 2×21223681² = 900889270379522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21223651) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 385 + ... + 6526.

It is an arithmetic number, because the mean of its divisors is an integer number (2757888).

Almost surely, 2^21223681 is an apocalyptic number.

It is an amenable number.

21223681 is a deficient number, since it is larger than the sum of its proper divisors (839423).

21223681 is an equidigital number, since it uses as much as digits as its factorization.

21223681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7031.

The product of its digits is 1152, while the sum is 25.

The square root of 21223681 is about 4606.9166478242. The cubic root of 21223681 is about 276.8685140146.

Adding to 21223681 its reverse (18632212), we get a palindrome (39855893).

It can be divided in two parts, 21223 and 681, that added together give a square (21904 = 148²).

The spelling of 21223681 in words is "twenty-one million, two hundred twenty-three thousand, six hundred eighty-one".