21206319 has 4 divisors (see below), whose sum is σ = 28275096. Its totient is φ = 14137544.

The previous prime is 21206303. The next prime is 21206323. The reversal of 21206319 is 91360212.

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 21206319 - 2⁴ = 21206303 is a prime.

It is a super-2 number, since 2×21206319² = 899415931059522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3534384 + ... + 3534389.

It is an arithmetic number, because the mean of its divisors is an integer number (7068774).

Almost surely, 2^21206319 is an apocalyptic number.

21206319 is a deficient number, since it is larger than the sum of its proper divisors (7068777).

21206319 is an equidigital number, since it uses as much as digits as its factorization.

21206319 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7068776.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21206319 is about 4605.0319217135. The cubic root of 21206319 is about 276.7929961293.

The spelling of 21206319 in words is "twenty-one million, two hundred six thousand, three hundred nineteen".