72817721 has 2 divisors, whose sum is σ = 72817722. Its totient is φ = 72817720.

The previous prime is 72817687. The next prime is 72817727. The reversal of 72817721 is 12771827.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 61795321 + 11022400 = 7861^2 + 3320^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72817721 is a prime.

It is not a weakly prime, because it can be changed into another prime (72817727) 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, 36408860 + 36408861.

It is an arithmetic number, because the mean of its divisors is an integer number (36408861).

Almost surely, 2^72817721 is an apocalyptic number.

It is an amenable number.

72817721 is a deficient number, since it is larger than the sum of its proper divisors (1).

72817721 is an equidigital number, since it uses as much as digits as its factorization.

72817721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10976, while the sum is 35.

The square root of 72817721 is about 8533.3300065098. The cubic root of 72817721 is about 417.5857731907.

The spelling of 72817721 in words is "seventy-two million, eight hundred seventeen thousand, seven hundred twenty-one".