72218309 has 2 divisors, whose sum is σ = 72218310. Its totient is φ = 72218308.

The previous prime is 72218287. The next prime is 72218353. The reversal of 72218309 is 90381227.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 70930084 + 1288225 = 8422^2 + 1135^2 .

It is a cyclic number.

It is not a de Polignac number, because 72218309 - 2¹² = 72214213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72218369) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36109154 + 36109155.

It is an arithmetic number, because the mean of its divisors is an integer number (36109155).

Almost surely, 2^72218309 is an apocalyptic number.

It is an amenable number.

72218309 is a deficient number, since it is larger than the sum of its proper divisors (1).

72218309 is an equidigital number, since it uses as much as digits as its factorization.

72218309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 72218309 is about 8498.1356190637. The cubic root of 72218309 is about 416.4368042730.

It can be divided in two parts, 72218 and 309, that added together give a palindrome (72527).

The spelling of 72218309 in words is "seventy-two million, two hundred eighteen thousand, three hundred nine".