21400843 has 4 divisors (see below), whose sum is σ = 21469968. Its totient is φ = 21331720.

The previous prime is 21400831. The next prime is 21400849. The reversal of 21400843 is 34800412.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21400843 is a prime.

It is a super-2 number, since 2×21400843² = 915992162221298, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21400849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34096 + ... + 34717.

It is an arithmetic number, because the mean of its divisors is an integer number (5367492).

Almost surely, 2^21400843 is an apocalyptic number.

21400843 is a deficient number, since it is larger than the sum of its proper divisors (69125).

21400843 is an equidigital number, since it uses as much as digits as its factorization.

21400843 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69124.

The product of its (nonzero) digits is 768, while the sum is 22.

The square root of 21400843 is about 4626.1045167614. The cubic root of 21400843 is about 277.6367553629.

The spelling of 21400843 in words is "twenty-one million, four hundred thousand, eight hundred forty-three".