663607561 has 4 divisors (see below), whose sum is σ = 663662800. Its totient is φ = 663552324.

The previous prime is 663607559. The next prime is 663607577. The reversal of 663607561 is 165706366.

663607561 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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 663607561 - 2¹ = 663607559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (663607501) 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, 1131 + ... + 36448.

It is an arithmetic number, because the mean of its divisors is an integer number (165915700).

Almost surely, 2^663607561 is an apocalyptic number.

It is an amenable number.

663607561 is a deficient number, since it is larger than the sum of its proper divisors (55239).

663607561 is a wasteful number, since it uses less digits than its factorization.

663607561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55238.

The product of its (nonzero) digits is 136080, while the sum is 40.

The square root of 663607561 is about 25760.5815345850. The cubic root of 663607561 is about 872.2422282659.

The spelling of 663607561 in words is "six hundred sixty-three million, six hundred seven thousand, five hundred sixty-one".