72505721 has 2 divisors, whose sum is σ = 72505722. Its totient is φ = 72505720.

The previous prime is 72505711. The next prime is 72505723. The reversal of 72505721 is 12750527.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64320400 + 8185321 = 8020^2 + 2861^2 .

It is a cyclic number.

It is not a de Polignac number, because 72505721 - 2²² = 68311417 is a prime.

It is a Sophie Germain prime.

Together with 72505723, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (72505723) 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, 36252860 + 36252861.

It is an arithmetic number, because the mean of its divisors is an integer number (36252861).

Almost surely, 2^72505721 is an apocalyptic number.

It is an amenable number.

72505721 is a deficient number, since it is larger than the sum of its proper divisors (1).

72505721 is an equidigital number, since it uses as much as digits as its factorization.

72505721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4900, while the sum is 29.

The square root of 72505721 is about 8515.0291250236. The cubic root of 72505721 is about 416.9885134290.

The spelling of 72505721 in words is "seventy-two million, five hundred five thousand, seven hundred twenty-one".