21309319 has 2 divisors, whose sum is σ = 21309320. Its totient is φ = 21309318.

The previous prime is 21309289. The next prime is 21309331. The reversal of 21309319 is 91390312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21309319 - 2¹¹ = 21307271 is a prime.

It is a super-2 number, since 2×21309319² = 908174152487522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21309019) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10654659 + 10654660.

It is an arithmetic number, because the mean of its divisors is an integer number (10654660).

Almost surely, 2^21309319 is an apocalyptic number.

21309319 is a deficient number, since it is larger than the sum of its proper divisors (1).

21309319 is an equidigital number, since it uses as much as digits as its factorization.

21309319 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1458, while the sum is 28.

The square root of 21309319 is about 4616.2017936828. The cubic root of 21309319 is about 277.2404043629.

It can be divided in two parts, 2130 and 9319, that added together give a square (11449 = 107²).

The spelling of 21309319 in words is "twenty-one million, three hundred nine thousand, three hundred nineteen".