915387721 has 2 divisors, whose sum is σ = 915387722. Its totient is φ = 915387720.

The previous prime is 915387703. The next prime is 915387727. The reversal of 915387721 is 127783519.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 908178496 + 7209225 = 30136^2 + 2685^2 .

It is a cyclic number.

It is not a de Polignac number, because 915387721 - 2¹¹ = 915385673 is a prime.

It is not a weakly prime, because it can be changed into another prime (915387727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 457693860 + 457693861.

It is an arithmetic number, because the mean of its divisors is an integer number (457693861).

Almost surely, 2^915387721 is an apocalyptic number.

It is an amenable number.

915387721 is a deficient number, since it is larger than the sum of its proper divisors (1).

915387721 is an equidigital number, since it uses as much as digits as its factorization.

915387721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 105840, while the sum is 43.

The square root of 915387721 is about 30255.3750761745. The cubic root of 915387721 is about 970.9607942104.

The spelling of 915387721 in words is "nine hundred fifteen million, three hundred eighty-seven thousand, seven hundred twenty-one".