661304857 has 4 divisors (see below), whose sum is σ = 661366836. Its totient is φ = 661242880.

The previous prime is 661304849. The next prime is 661304909. The reversal of 661304857 is 758403166.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 758403166 = 2 ⋅379201583.

It can be written as a sum of positive squares in 2 ways, for example, as 118461456 + 542843401 = 10884^2 + 23299^2 .

It is a cyclic number.

It is not a de Polignac number, because 661304857 - 2³ = 661304849 is a prime.

It is a super-2 number, since 2×661304857² = 874648227783580898, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661304837) 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, 10444 + ... + 37837.

It is an arithmetic number, because the mean of its divisors is an integer number (165341709).

Almost surely, 2^661304857 is an apocalyptic number.

It is an amenable number.

661304857 is a deficient number, since it is larger than the sum of its proper divisors (61979).

661304857 is a wasteful number, since it uses less digits than its factorization.

661304857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61978.

The product of its (nonzero) digits is 120960, while the sum is 40.

The square root of 661304857 is about 25715.8483624398. The cubic root of 661304857 is about 871.2321717989.

The spelling of 661304857 in words is "six hundred sixty-one million, three hundred four thousand, eight hundred fifty-seven".