21212843 has 4 divisors (see below), whose sum is σ = 21481440. Its totient is φ = 20944248.

The previous prime is 21212837. The next prime is 21212861. The reversal of 21212843 is 34821212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21212843 - 2²⁰ = 20164267 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21212143) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134180 + ... + 134337.

It is an arithmetic number, because the mean of its divisors is an integer number (5370360).

Almost surely, 2^21212843 is an apocalyptic number.

21212843 is a deficient number, since it is larger than the sum of its proper divisors (268597).

21212843 is an equidigital number, since it uses as much as digits as its factorization.

21212843 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268596.

The product of its digits is 768, while the sum is 23.

The square root of 21212843 is about 4605.7402228089. The cubic root of 21212843 is about 276.8213778011.

The spelling of 21212843 in words is "twenty-one million, two hundred twelve thousand, eight hundred forty-three".