663656421 has 36 divisors (see below), whose sum is σ = 983313632. Its totient is φ = 398031744.

The previous prime is 663656417. The next prime is 663656437. The reversal of 663656421 is 124656366.

It is not a de Polignac number, because 663656421 - 2² = 663656417 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 663656421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (663656471) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 457920 + ... + 459366.

Almost surely, 2^663656421 is an apocalyptic number.

It is an amenable number.

663656421 is a deficient number, since it is larger than the sum of its proper divisors (319657211).

663656421 is a wasteful number, since it uses less digits than its factorization.

663656421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1530 (or 1490 counting only the distinct ones).

The product of its digits is 155520, while the sum is 39.

The square root of 663656421 is about 25761.5298652856. The cubic root of 663656421 is about 872.2636348481.

The spelling of 663656421 in words is "six hundred sixty-three million, six hundred fifty-six thousand, four hundred twenty-one".