21743681 has 8 divisors (see below), whose sum is σ = 22417824. Its totient is φ = 21077280.

The previous prime is 21743677. The next prime is 21743693. The reversal of 21743681 is 18634712.

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 21743681 - 2² = 21743677 is a prime.

It is a super-2 number, since 2×21743681² = 945575326859522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21743611) 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, 4046 + ... + 7736.

It is an arithmetic number, because the mean of its divisors is an integer number (2802228).

Almost surely, 2^21743681 is an apocalyptic number.

It is an amenable number.

21743681 is a deficient number, since it is larger than the sum of its proper divisors (674143).

21743681 is a wasteful number, since it uses less digits than its factorization.

21743681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3871.

The product of its digits is 8064, while the sum is 32.

The square root of 21743681 is about 4663.0120094205. The cubic root of 21743681 is about 279.1114733786. Note that the first 3 decimals are identical.

The spelling of 21743681 in words is "twenty-one million, seven hundred forty-three thousand, six hundred eighty-one".