72745721 has 2 divisors, whose sum is σ = 72745722. Its totient is φ = 72745720.

The previous prime is 72745693. The next prime is 72745781. The reversal of 72745721 is 12754727.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 62980096 + 9765625 = 7936^2 + 3125^2 .

It is an emirp because it is prime and its reverse (12754727) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 72745721 - 2⁶ = 72745657 is a prime.

It is not a weakly prime, because it can be changed into another prime (72745781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36372860 + 36372861.

It is an arithmetic number, because the mean of its divisors is an integer number (36372861).

Almost surely, 2^72745721 is an apocalyptic number.

It is an amenable number.

72745721 is a deficient number, since it is larger than the sum of its proper divisors (1).

72745721 is an equidigital number, since it uses as much as digits as its factorization.

72745721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27440, while the sum is 35.

The square root of 72745721 is about 8529.1102115051. The cubic root of 72745721 is about 417.4480956665.

The spelling of 72745721 in words is "seventy-two million, seven hundred forty-five thousand, seven hundred twenty-one".