245657721 has 4 divisors (see below), whose sum is σ = 327543632. Its totient is φ = 163771812.

The previous prime is 245657693. The next prime is 245657729. The reversal of 245657721 is 127756542.

245657721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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.

It is not a de Polignac number, because 245657721 - 2¹³ = 245649529 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 245657721.

It is not an unprimeable number, because it can be changed into a prime (245657729) 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, 40942951 + ... + 40942956.

It is an arithmetic number, because the mean of its divisors is an integer number (81885908).

Almost surely, 2^245657721 is an apocalyptic number.

It is an amenable number.

245657721 is a deficient number, since it is larger than the sum of its proper divisors (81885911).

245657721 is an equidigital number, since it uses as much as digits as its factorization.

245657721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81885910.

The product of its digits is 117600, while the sum is 39.

The square root of 245657721 is about 15673.4718872367. The cubic root of 245657721 is about 626.2919162704.

The spelling of 245657721 in words is "two hundred forty-five million, six hundred fifty-seven thousand, seven hundred twenty-one".