663729521 has 16 divisors (see below), whose sum is σ = 864952704. Its totient is φ = 494256384.

The previous prime is 663729511. The next prime is 663729533. The reversal of 663729521 is 125927366.

It is a cyclic number.

It is not a de Polignac number, because 663729521 - 2¹⁰ = 663728497 is a prime.

It is a Smith number, since the sum of its digits (41) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (663729511) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 212975 + ... + 216068.

It is an arithmetic number, because the mean of its divisors is an integer number (54059544).

Almost surely, 2^663729521 is an apocalyptic number.

It is an amenable number.

663729521 is a deficient number, since it is larger than the sum of its proper divisors (201223183).

663729521 is a wasteful number, since it uses less digits than its factorization.

663729521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 429080.

The product of its digits is 136080, while the sum is 41.

The square root of 663729521 is about 25762.9486084183. The cubic root of 663729521 is about 872.2956595166.

The spelling of 663729521 in words is "six hundred sixty-three million, seven hundred twenty-nine thousand, five hundred twenty-one".