663664561 has 8 divisors (see below), whose sum is σ = 759461184. Its totient is φ = 568114800.

The previous prime is 663664549. The next prime is 663664571. The reversal of 663664561 is 165466366.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 663664561 - 2¹³ = 663656369 is a prime.

It is a super-4 number, since 4×663664561⁴ (a number of 36 digits) contains 4444 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (663664501) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 55915 + ... + 66736.

It is an arithmetic number, because the mean of its divisors is an integer number (94932648).

Almost surely, 2^663664561 is an apocalyptic number.

It is an amenable number.

663664561 is a deficient number, since it is larger than the sum of its proper divisors (95796623).

663664561 is a wasteful number, since it uses less digits than its factorization.

663664561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123431.

The product of its digits is 466560, while the sum is 43.

The square root of 663664561 is about 25761.6878523128. The cubic root of 663664561 is about 872.2672010493.

It can be divided in two parts, 663664 and 561, that added together give a square (664225 = 815²).

The spelling of 663664561 in words is "six hundred sixty-three million, six hundred sixty-four thousand, five hundred sixty-one".