3966661221 has 16 divisors (see below), whose sum is σ = 5601809664. Its totient is φ = 2488077824.

The previous prime is 3966661211. The next prime is 3966661241. The reversal of 3966661221 is 1221666693.

It is a cyclic number.

It is not a de Polignac number, because 3966661221 - 2¹⁰ = 3966660197 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3966661211) 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, 172420 + ... + 194066.

It is an arithmetic number, because the mean of its divisors is an integer number (350113104).

Almost surely, 2^3966661221 is an apocalyptic number.

It is an amenable number.

3966661221 is a deficient number, since it is larger than the sum of its proper divisors (1635148443).

3966661221 is a wasteful number, since it uses less digits than its factorization.

3966661221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25260.

The product of its digits is 139968, while the sum is 42.

The square root of 3966661221 is about 62981.4355266693. The cubic root of 3966661221 is about 1582.9785747121.

The spelling of 3966661221 in words is "three billion, nine hundred sixty-six million, six hundred sixty-one thousand, two hundred twenty-one".