72211721 has 2 divisors, whose sum is σ = 72211722. Its totient is φ = 72211720.

The previous prime is 72211709. The next prime is 72211759. The reversal of 72211721 is 12711227.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 71233600 + 978121 = 8440^2 + 989^2 .

It is an emirp because it is prime and its reverse (12711227) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72211721 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (72211781) 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 as a sum of consecutive naturals, namely, 36105860 + 36105861.

It is an arithmetic number, because the mean of its divisors is an integer number (36105861).

Almost surely, 2^72211721 is an apocalyptic number.

It is an amenable number.

72211721 is a deficient number, since it is larger than the sum of its proper divisors (1).

72211721 is an equidigital number, since it uses as much as digits as its factorization.

72211721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 392, while the sum is 23.

The square root of 72211721 is about 8497.7479957928. The cubic root of 72211721 is about 416.4241409602.

Adding to 72211721 its reverse (12711227), we get a palindrome (84922948).

The spelling of 72211721 in words is "seventy-two million, two hundred eleven thousand, seven hundred twenty-one".