663556521 has 8 divisors (see below), whose sum is σ = 905317600. Its totient is φ = 432083232.

The previous prime is 663556507. The next prime is 663556577. The reversal of 663556521 is 125655366.

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

It is not a de Polignac number, because 663556521 - 2¹³ = 663548329 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 663556521.

It is not an unprimeable number, because it can be changed into a prime (663551521) 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, 2571796 + ... + 2572053.

It is an arithmetic number, because the mean of its divisors is an integer number (113164700).

Almost surely, 2^663556521 is an apocalyptic number.

It is an amenable number.

663556521 is a deficient number, since it is larger than the sum of its proper divisors (241761079).

663556521 is a wasteful number, since it uses less digits than its factorization.

663556521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5143895.

The product of its digits is 162000, while the sum is 39.

The square root of 663556521 is about 25759.5908546700. The cubic root of 663556521 is about 872.2198654582.

The spelling of 663556521 in words is "six hundred sixty-three million, five hundred fifty-six thousand, five hundred twenty-one".