21656843 has 6 divisors (see below), whose sum is σ = 23451084. Its totient is φ = 19990776.

The previous prime is 21656839. The next prime is 21656849. The reversal of 21656843 is 34865612.

It is not a de Polignac number, because 21656843 - 2² = 21656839 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21656849) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 63905 + ... + 64242.

It is an arithmetic number, because the mean of its divisors is an integer number (3908514).

Almost surely, 2^21656843 is an apocalyptic number.

21656843 is a deficient number, since it is larger than the sum of its proper divisors (1794241).

21656843 is a wasteful number, since it uses less digits than its factorization.

21656843 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128173 (or 128160 counting only the distinct ones).

The product of its digits is 34560, while the sum is 35.

The square root of 21656843 is about 4653.6913305461. The cubic root of 21656843 is about 278.7394140242.

The spelling of 21656843 in words is "twenty-one million, six hundred fifty-six thousand, eight hundred forty-three".