72578221 has 2 divisors, whose sum is σ = 72578222. Its totient is φ = 72578220.

The previous prime is 72578197. The next prime is 72578237. The reversal of 72578221 is 12287527.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 69973225 + 2604996 = 8365^2 + 1614^2 .

It is a cyclic number.

It is not a de Polignac number, because 72578221 - 2⁵ = 72578189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (72578021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36289110 + 36289111.

It is an arithmetic number, because the mean of its divisors is an integer number (36289111).

Almost surely, 2^72578221 is an apocalyptic number.

It is an amenable number.

72578221 is a deficient number, since it is larger than the sum of its proper divisors (1).

72578221 is an equidigital number, since it uses as much as digits as its factorization.

72578221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15680, while the sum is 34.

The square root of 72578221 is about 8519.2852399717. The cubic root of 72578221 is about 417.1274523337.

The spelling of 72578221 in words is "seventy-two million, five hundred seventy-eight thousand, two hundred twenty-one".