21983681 has 4 divisors (see below), whose sum is σ = 22692864. Its totient is φ = 21274500.

The previous prime is 21983671. The next prime is 21983683. The reversal of 21983681 is 18638912.

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 21983681 - 2⁶ = 21983617 is a prime.

It is a super-2 number, since 2×21983681² = 966564460619522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21983683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 354545 + ... + 354606.

It is an arithmetic number, because the mean of its divisors is an integer number (5673216).

Almost surely, 2^21983681 is an apocalyptic number.

It is an amenable number.

21983681 is a deficient number, since it is larger than the sum of its proper divisors (709183).

21983681 is an equidigital number, since it uses as much as digits as its factorization.

21983681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 709182.

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

The square root of 21983681 is about 4688.6758258596. The cubic root of 21983681 is about 280.1346333826.

The spelling of 21983681 in words is "twenty-one million, nine hundred eighty-three thousand, six hundred eighty-one".