21213679 has 2 divisors, whose sum is σ = 21213680. Its totient is φ = 21213678.

The previous prime is 21213677. The next prime is 21213697. The reversal of 21213679 is 97631212.

Together with next prime (21213697) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21213679 - 2¹ = 21213677 is a prime.

Together with 21213677, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21213679.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21213677) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606839 + 10606840.

It is an arithmetic number, because the mean of its divisors is an integer number (10606840).

Almost surely, 2^21213679 is an apocalyptic number.

21213679 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213679 is an equidigital number, since it uses as much as digits as its factorization.

21213679 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4536, while the sum is 31.

The square root of 21213679 is about 4605.8309782275. The cubic root of 21213679 is about 276.8250142716.

The spelling of 21213679 in words is "twenty-one million, two hundred thirteen thousand, six hundred seventy-nine".