663729221 has 4 divisors (see below), whose sum is σ = 664045452. Its totient is φ = 663412992.

The previous prime is 663729191. The next prime is 663729233. The reversal of 663729221 is 122927366.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 80748196 + 582981025 = 8986^2 + 24145^2 .

It is a cyclic number.

It is not a de Polignac number, because 663729221 - 2²⁶ = 596620357 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (663729271) 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, 154946 + ... + 159171.

It is an arithmetic number, because the mean of its divisors is an integer number (166011363).

Almost surely, 2^663729221 is an apocalyptic number.

It is an amenable number.

663729221 is a deficient number, since it is larger than the sum of its proper divisors (316231).

663729221 is a wasteful number, since it uses less digits than its factorization.

663729221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 316230.

The product of its digits is 54432, while the sum is 38.

The square root of 663729221 is about 25762.9427861027. The cubic root of 663729221 is about 872.2955280933.

The spelling of 663729221 in words is "six hundred sixty-three million, seven hundred twenty-nine thousand, two hundred twenty-one".