315505721 has 4 divisors (see below), whose sum is σ = 315567744. Its totient is φ = 315443700.

The previous prime is 315505691. The next prime is 315505739. The reversal of 315505721 is 127505513.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 127505513 = 83 ⋅1536211.

It is a cyclic number.

It is not a de Polignac number, because 315505721 - 2¹⁰ = 315504697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (315505741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22625 + ... + 33806.

It is an arithmetic number, because the mean of its divisors is an integer number (78891936).

Almost surely, 2^315505721 is an apocalyptic number.

It is an amenable number.

315505721 is a deficient number, since it is larger than the sum of its proper divisors (62023).

315505721 is an equidigital number, since it uses as much as digits as its factorization.

315505721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62022.

The product of its (nonzero) digits is 5250, while the sum is 29.

The square root of 315505721 is about 17762.4807107566. The cubic root of 315505721 is about 680.7731409560.

The spelling of 315505721 in words is "three hundred fifteen million, five hundred five thousand, seven hundred twenty-one".